Rome's Lost Empire

'The Roman Empire.

'With its Coliseum,

'its gladiators

'and its ancient cities...

'..frozen in time.

'No other power dominated the planet for so long.

'But what are the secrets that helped Rome rule?

'It remains one of history's greatest riddles.

'Until now.'

There are about 60 features that have appeared

which show up in these red circles.

'By using satellites,

'one archaeologist will uncover a Rome

'that no-one knew existed.

'Finding buried settlements,

'forgotten forts,

'and lost amphitheatres.'

It's never been discovered before?

As far as I know, it is a completely new structure.

'I'm Dan Snow,

'a broadcaster with a passion for history.'

50,000 people would have packed into here.

'This is my chance to join this revolution in archaeology.'

Wow, that's wonderful! That looks like a Roman fort.

'Together, we'll journey to the four corners of the Roman Empire.'

There's a fork in the road here, do you want me to right or left?

I think we just continue on ahead, according to my GPS.

'From the mountains and rivers of Europe...'

Can you see? I'm touching it now.

'..to the hot deserts of the Middle East.'

It's a very special place for me

because I came here with my mum and dad when I was a kid.

'Across the vast interior of Africa...'

What the satellites are showing us is just...

There's so much more left to find.

'..to the glory of Rome itself.'

That is awesome!

'And, guided by best Roman archaeologists in the world...'

How amazing is this view?

'..tell the real story...

'..of how Rome ruled.'

'Our journey begins not in the old world but the new.

'In America's Deep South.'

I've always been absolutely fascinated by the Roman Empire.

I think it was cos as a kid my mum and dad dragged me

round the Roman sites, like Hadrian's Wall,

and that really fired my imagination.

And then as I've grown older,

I've studied the Roman Army tactics and technology,

fighting those battles the legend of which

echoed down across the centuries.

But there's always been one thing about Rome

that's absolutely intrigued me.

'At its height, the Roman Empire was vast.

'Pushing out from Rome,

'through modern-day Germany, France and Spain,

'up into drizzle-soaked Northern England.

'Stretching eastwards over the mountains of Middle Europe...

'..all the way to the sun-baked deserts of Syria and Jordan.

'And south, across the immense, rich plains of the North African coast.

'This was an Empire that covered five million square miles

'and had a population of at least 60 million people.

'That left Rome's army, of around 300,000 troops,

'massively outnumbered.

'200 to one.'

Yes, the Roman Army was the best in the world.

But, at the same time, how could Rome rule over such a vast empire

with such a small number of professional troops?

It's a question that's always baffled me.

That's why I've come to Birmingham, Alabama, in the United States

to meet a woman who I think is going to help me find an answer.

'Dr Sarah Parcak is an associate professor of archaeology

'at Alabama State University.'

There have been a number of cases throughout history

where people have used identity...

'By day, she's a regular college lecturer.'

..truly crusader period. I mean, it had a big arrow through its chest.

'But at night, it's a different story.'

When I was a small girl,

I always used to imagine myself on a rocket ship.

I'm going to be finding other planets,

we're going to be meeting aliens.

Here we are, we're in this lab.

You know, it's like... it's like I'm in that spaceship.

'Sarah is a pioneer in the new science of space archaeology.'

The vehicle for exploration is a computer.

There are thousands...hundreds of thousands of archaeological sites

and features all over the world that haven't been found yet.

And I know they're out there to be found.

And if you hit the right button, it will just pop out in front of you.

That moment of discovery, that a-ha moment,

that's like you're landing the ship on another planet.

And the doors are opening for the first time

onto a completely new world.

'She's using satellites orbiting 500 miles above the earth.

'They are equipped with high-resolution cameras

'developed by the military for spying.

'These satellites can pinpoint objects

'less than a metre in diameter on the earth's surface.

'12 months ago, Sarah had huge success in Egypt...'

For the whole of upper Egypt, I have found over 1,200 ancient sites.

'..uncovering long-lost temples, tombs and even pyramids...

'..using satellites to change our understanding

'of Egyptian civilisation for ever.'

All right, Dan. So I want to show you how this technology works.

So we're going to go to an Egyptian settlement.

And what you're really seeing is the equivalent of

an aerial photograph but taken from space.

And what we do is, we combine the higher resolution technology

with infrared technology to get this.

-Wow.

-So really what you're seeing

are the outlines of buildings, structures and even ancient streets.

That's like a map of downtown Manhattan.

But, you know, I have to say, this is really the technology at its best.

'This time, the task will be much harder.

'The Roman Empire was six times bigger than Egypt

'and not simply desert,

'but a multitude of complex landscapes and terrains.'

There's an area here in Romania,

and we're very, very interested in this area.

We know that something interesting might be here.

But, unfortunately, there's a problem.

There are a lot of trees.

There are many trees, and satellites simply cannot see through trees,

it's impossible.

OK, that is a challenge.

This is something we are working through right now.

OK, this is the thing, the bottom line is,

are you going to come with me around the Roman Empire?

And can you and your technology help solve this central riddle

of how this empire was ruled?

Because if you deliver, if this technology delivers,

these could be some of the biggest breakthroughs in Roman history

for hundreds of years.

Yeah, I am definitely up for this challenge,

but this technology, it's not without its limitations.

So, on the one hand, I'm really, really excited

about what we might possibly find, but on the other hand,

I'm also pretty, pretty nervous.

I guess there is that jeopardy of finding out whether or not

I really am an expert at doing this.

Running is where I can really clear my head

and allow myself time to think.

I am determined.

I'm a pretty focused person once I set my mind to something.

I'll just run into a brick wall until it falls over.

That's not always wise,

because you end up getting quite bruised and bloodied.

But eventually there are cracks that show up.

'Our quest begins in the capital city of Italy.

'Rome, where else?

'At the height of the Roman Empire, roughly the first two centuries AD,

'this was the most extraordinary city on the planet.

'Crammed with glittering palaces, triumphal arches and amphitheatres.'

-There you go.

-That is awesome.

-The Coliseum.

'It seems the obvious place to begin. Or is it?

'We are heading 20 miles west, along the River Tiber...

'..to a place now long forgotten.

'It's said to be the lost jewel.

'The glittering secret behind Rome's success.

'Which could provide vital clues...

That is awesome.

'..as to how it ruled its vast Empire.

'This is Portus...

'..the once-great harbour of Rome.

'For 500 years, the most important seaport in the entire world.

'At its heart was a gigantic hexagonal basin,

'still here today...

'..big enough to berth 150 ships.

'Which, 2,000 years ago, was attached to an even great basin,

'six times as large.

'A series of canals have been identified

'which once linked the harbour to Rome.

'But there are huge gaps in our knowledge.

'And to know how this port complex actually worked might give us

'a better understanding of what made the Empire as a whole tick.

'But it's a mind-boggling challenge.

'Over thousands of years, the sea has receded three miles to the west

'and much of the harbour is now buried

'beneath a chaos of suburbs, flyovers and roads

'on the edge of Fiumicino Airport.

'While Sarah sets up her base of operations,

'I'm off to meet the world expert on Portus,

'the renowned British archaeologist Professor Simon Keay.

'He's here leading a team

'which, once the weather breaks,

'hopes to excavate the site.

'In the meantime I'm grabbing a moment to learn more about the harbour.'

Why did Rome need this great big port right next door to it?

Well, that's actually a very good question.

I think you have to remember that

Rome was an exceptional pre-industrial city,

nearly a million people.

And a million people living in an imperial capital.

So you need food on an unparalleled scale,

in a pre-industrial society.

You also need all the effects,

materials that dignify an imperial capital.

Like marble, silks, gold statues and everything else.

'Simon has spent his career building up a picture of how Portus worked.

'But, after years of digging, it's still not making sense.

'He's hoping that Sarah's technology can help complete the puzzle.'

What would you like Sarah to look for?

What would it be great if she found?

What she really needs to focus on is canals, primarily,

because what we don't know so much about is how all this worked.

But I guess the real special thing to find, it would be too much to ask,

but one just hopes that maybe by looking at satellite imagery

we can add...we can add more to or perhaps even find

the great lighthouse of Portus.

'The lighthouse of Portus

'is one of the lost Wonders of the Ancient World

'and was said to be visible from over 20 miles out to sea.

'Sought after by archaeologists for centuries,

'it's considered the ultimate symbol of Roman power.

'And finding hard physical evidence for its existence

'would be one of the greatest finds of Simon's career.'

-Sarah, how's it going? You've been here all night.

-Hey, Dan.

-Burning the midnight oil.

-Looking good?

Well, not, er...not quite.

I mean, this is, this is a really, really difficult landscape.

You've got tons of urbanisation, which you can see here.

You know, I've been looking up here

and, you know, things that I think might possibly be ancient

turn out to be modern the more I look at them, so

it's pretty complicated and I'm still trying to get my head around it.

I don't really understand this, there's not much I can do to help,

-so I'm going to get some sleep, you keep at it.

-Lucky you, Dan.

'After working all night, Sarah has found...

'nothing.

'And the reality of what she's set out to do finally hits home.'

We're in the middle of this blighted urban wasteland.

I keep thinking, how is it that the satellite imagery

can possibly show us what might be here?

There's really nothing here that's visible

that hints of the glory of this once-great port of Rome.

Maybe I'm naive in thinking that it will work this time.

Maybe I have bitten off more than I can chew.

'We are not giving up on Portus.

'But with Sarah clearly struggling with her satellites,

'it's time for me to take temporary charge.

'To understand how Rome ruled its vast Empire,

'there are several key areas to look at.

'But for me, as a military historian,

'there is only one place now to go.

'Transylvania.

'Dark. Impenetrable.

'And in the Second Century AD,

'a mountain kingdom ruled by a tribe the Romans dismissed as barbarians.

'We're leaving Portus for now and heading to Transylvania,

'part of modern-day Romania.

'Because what happened here is the best example I know

'of the Roman Army at its most ruthless.

'From deep in the forest, a barbarian tribe called the Dacians

'were getting too big for their boots -

'raiding Roman territory,

'stealing livestock and women,

'and giving the greatest empire on earth

'the proverbial two-finger salute.

'By themselves the Dacian barbarians posed no real threat.

'But Rome had built its reputation on ruthlessness.

'Rome understood that, if it showed any sign of weakness,

'similar rebellions could rise up right across the Empire.

'The Dacians had to be made an example of.

'Including their renegade leader.

'Now a martyr, and symbol of rebellion.

'This is Decebalus.

'King of the Dacians.

'Rome had military commitments right across its vast empire,

'but it knew it had to prove a point.

'It threw an astonishing 60,000 men at the Dacians,

'and in doing so sent out a clear message.

'Never mess with Rome.

'But to get at the Dacians,

'the Romans first had to cross

'one of the most formidable natural barriers in the entire world.

'Nearly a mile wide, fast flowing, with murderous currents -

'the mighty Danube river.

'What's most remarkable is how they did it.'

It's going to be a very challenging dive today.

The Danube is difficult at the best of times.

You can see the way this current swirls around, racing down there towards the Black Sea,

and the visibility looks particularly bad.

So lots of things to worry about.

So we've managed to notify International Shipping

and it's time to go for it.

OK, Johnny?

Are we ready to go on this, gentlemen?

It's quite hard going, there's a lot of current.

Very, very slow.

You might want to try going down to the base of the river,

just so you can crawl along, over, so I can give you directions.

OK, I'm getting close to what looks like the bottom here.

Wow, there's a lot of current down here.

Making very slow progress.

The water's whipping around you pretty quickly,

be careful down there, Dan.

Just dragging myself along the floor of this riverbed.

There's a lot of current.

It looks like it should be here somewhere, close by.

Why don't you try going about three or four metres to your right?

I think you're a bit off at the moment.

Sarah, I can see...

I can see something.

It's very hard to tell through this incredibly bad visibility.

I'm beginning to make out the faint outline of something.

Describe to me what you're seeing, Dan.

Can you see? I'm touching it now.

It's clearly what appears to be the footings of a bridge.

Some brickwork. You can see the mortar. It's pretty overgrown now.

But I think what we're seeing here is the evidence of

the Roman bridge across the Danube.

'And not just any old bridge.

'It was the longest bridge in the entire world...

'..nearly a mile from bank to bank.

'One of the biggest works of military architecture

'in the history of the Roman Empire.'

Well, that was... that was just incredible.

Definitely saw the footings of the Roman bridge.

It's an incredible testament to the engineering prowess

of the Roman Army that, even after 2,000 years

on one of the fastest and busiest rivers on the planet,

it's still there.

This really was a titanic undertaking,

and it took them around about two years. A long time.

But actually, I think the Romans would have potentially

seen that as an advantage.

There's something crushingly inevitable about the slow progress

of this bridge across this mighty river.

You can just imagine the Dacians standing on the other side,

seeing it edge closer week by week.

And it was a message designed not just for the Dacians

on the other side of the Danube,

but for people all over the Empire and beyond.

This told people that no mountain was too high,

no river was too wide.

Rome would spend any amount of money

and deploy any number of soldiers to enforce its domination.

And by building the longest bridge on the planet here on the Danube,

Rome was laying claim to mastery of the known world.

'Once across the river, it's believed that the main contingent

'of the Roman Army, led by their all-conquering Emperor, Trajan,

'hacked and killed its way up the Jiu Valley,

'heading north,

'towards the barbarians' capital city, Sarmizegetusa.

'Or Sarmi for short.'

Sarah, I'm dying here. This car is tiny, I'm getting cramp.

Dan, you've got to stop complaining. We've got a long way to go.

-That's tough love, man.

-That's what you're getting from me.

'King Decabulus and his warriors were finally defeated here at Sarmi.

'Archaeologists believe after the war was over,

'the Romans suppressed outbreaks of sporadic violence

'with an occupying army.

'But how they achieved this isn't known.

'There could be clues buried beneath the undergrowth.

'But there's a problem.

'The whole area is completely carpeted in thick forest.

'And Sarah's satellites can't see through trees.

'Fortunately, all is not lost.

'This is new for Sarah.

'It's called LIDAR.

'A revolutionary technique used by the military

'to locate enemy targets in dense undergrowth.

'Here, she's looking for walls, ditches,

'anything that might shed light on how Rome kept the peace

'once the war was over.

'Rather than satellites, this involves an aeroplane,

'which fires up to 100,000 laser beams every second

'into the forest beneath.

'While the first beams hit the treetops,

'the last ones strike the forest floor.

'So, by removing that first pulse survey,

'scientists effectively remove the trees,

'revealing anything which might be hidden beneath.'

OK, Dan, here we are.

You're looking to the central part of the site of Sarmizegetusa.

'Dr Gelu Florea is head of archaeology at Cluj University.

'He has spent 26 years investigating Sarmi

'and is the number one world expert on the site.

'Having surveyed the whole area,

'it's time for Sarah to show Gelu the results.

'And he's in for a big surprise.'

Here we have a visual satellite image of Sarmi.

As you know far better than we do,

the area is very densely covered in trees

and unfortunately right now with satellite imagery

we can't see through trees.

So we used a new technology called LIDAR,

which is flown from an aeroplane

and sends down thousands of pulses of beams of light

and you can literally use that to peel away

the layers of vegetation.

And this is what we have.

It's beautiful. It's amazing.

I'll zoom in a little bit.

So what are we seeing here? Those lines are incredible.

It's a huge rampart, I think.

A rampart-like feature...

..that we never knew until now.

It's got that shape and everything.

It...it's beautiful. It's amazing, as a matter of fact.

You can, I mean, it does seem pretty clear,

not as clear here but it runs there.

No, it's absolutely clear on this side, on this side also, and here.

'What Sarah has discovered is completely new to Gelu.

'According to conventional thinking, when Sarmi fell,

'the Romans left behind a garrison of around 500 men,

'to hold the area and make it safe.

'But archaeologists have puzzled

'over how that could have been achieved with so few soldiers.

'It now looks like a massive man-made embankment

'enclosed the whole area,

'offering the mouth-watering possibility of fresh evidence

'into the extent of the Roman occupation.

'But we won't know the find is Roman until we see it on the ground.

'We're setting off on a long trek through deep forest.

'It's rough country, and our guides are taking no chances.

'We're not going to make it before nightfall,

'and Transylvania is the last place

'you want to be walking about after dark.'

What a nice campsite.

-Hello there.

-Hello.

-Want some bread?

-Bread would be great, thank you.

Want a piece?

-Bread?

-No, thanks.

Is there anything in kind of local folklore

connecting people here to the Romans?

Of course we say that looking at the ear lobe,

the ones who have a long ear lobe would be Romans,

and the ones who have small ones are Dacian.

Let's see what you've got?

Roman. Big emperor.

He has a long ear lobe, Roman.

What have I got?

You are certainly Dacian.

-I think I'm a Roman princess, that's for sure.

-You wish.

What do kids learn about the Romans in school?

Are they invaders, are they evil?

Or are they the founders of Romania?

No, in history books, Trajan and Decebalus, the leaders of the two nations,

they are the fathers of our nation,

so Trajan more important than Decapolis.

Earlier today I saw Jan was carrying a gun.

Why was he carrying a gun?

For bears. Why else?

'The following day the trek continues into the heart of an ancient forest.

'This is the original wild wood.

'Eventually we find proof on the ground

'that Sarah's find is indeed Roman.

'This is the evidence we have been seeking.'

I think this is the structure that we saw

-already on the on the photograph.

-It's very clear.

You can see it stretching off right the way down through,

it looks like a ditch and then a bank here.

What would this have been?

I think it's clearly an embankment of ramparts and that's why I think

it's part of a defensive structure. A Roman temporary camp.

What phase of Roman occupation do you think this was built in?

Well, it probably belongs to the Roman garrison

that was left here after the war.

I can't think of another purpose than to pacify the area,

to prevent any other skirmishes, to prevent a regrouping of forces

around these sacred places of the Dacians and so on.

So this is, they've won the war, now they're trying to win the peace?

Yes.

Sarah has finally found something.

And it's helping to rewrite history.

The 500-man Roman garrison was just part of a huge military camp...

..with enough space for a further 8,000 troops.

It shows for the first time how Rome really pacified the area.

Investing large amounts of troops

and thinking long term.

It wasn't enough to simply slaughter the Dacians and then leave.

To remove the menace, whole swathes of land had to be first made safe

and then incorporated into the Empire.

Imperial policy across the entire Roman world.

Dacia is just a terrifying example of just how the Roman Empire

invaded and occupied new territory.

When the Romans wanted to,

they could bring vast and ruthless military force to bear.

They invaded Dacia, they destroyed its army,

they wiped out its leadership

and then they set about the long and arduous task of pacification.

They hunted down insurgents, guerrilla fighters.

They destroyed religious sites like this,

anything that could provide the focus for anti-Roman resistance.

When you come here, you realise,

for all the wonderful art and architecture

that the Romans produced,

at its root, Rome was a brutal military super power.

And that was a fundamental reason for its supremacy.

Sarah is starting to have success. But the good news doesn't end there.

After months of searching, she thinks she's finally

had a breakthrough with the satellites too.

She thinks she's found something back in Italy

that, if true, could be groundbreaking.

Let's take another look at Portus, the great lost harbour of Rome.

Understanding how it worked might give us a new insight

into how the Roman Empire as a whole operated.

This is what archaeologists think happened.

Ships would crowd into the big basins...

..their cargo unloaded onto smaller boats...

..which was then moved by canal to the River Tiber,

and onward, along to the river, to Rome.

But there's a big hole in this theory.

With hundreds of ships on the water at any one time,

there must have been major bottlenecks,

crippling the whole transport network.

It's something that has puzzled archaeologists for decades.

Back in her lab in Italy,

Sarah thinks she may have found the answer.

So I'd like to show you an interesting thing that showed up

on the east bank of the Tiber.

It's about 280 metres long, about five metres wide.

Running slightly southwest by northeast.

You can see it running along just there.

Ah, now that's really interesting,

because that looks to me like it might be a canal.

Although, I must say, it's different to the other ones we found.

How was that different?

Well, all the other canals we have found to date

have been on the west side of the Tiber, close to the port...

Portus.

This canal is on the east side of the Tiber

and, perhaps more significantly, it's going in the direction of Rome.

What does it mean, that it's just heading off towards Rome?

For me, the significance is quite straightforward.

The fact that you have a new canal here suggests to me

that river barges may have avoided

this rather longer route up the Tiber

by going more directly to Rome.

And indeed, that helps us better understand

how the port system as a whole worked.

So, that's fantastic, well done.

To test whether the new canal is actually there

buried beneath tonnes of earth,

Simon and his team visit the site.

And the results of a geophysical survey are highly promising.

It looks like Sarah is right.

For a really eminent archaeologist like Simon who, you know,

has devoted so much of his career to working at Portus,

you know, seeing him get so excited about the science and be so

willing to not only embrace it, but test it on the ground and

think about the findings in terms of his long term research plans

for a site - that's awesome!

It's great to have this confirmation, it's really exciting, but for me

what's even more exciting is it's really helping to show just how far

the technology has come.

I feel like that's given me a lot of confidence.

I just absolutely cannot wait for what's next.

Sarah's satellites are helping to show how

this astonishing harbour landscape may actually have worked.

An inadequate transport system

could have left the people of Rome starving.

Grain, in particular, had to be kept dry

so the faster it could be moved, the better.

And this is how they might have achieved that.

Boats didn't have to travel all the way up the Tiber River,

they could go straight to Rome by Sarah's canal.

It's also helping me answer the bigger question

of how Rome kept control of its vast Empire.

We associate canals with the Industrial Revolution

but the Romans were building them 2000 years ago

and not just in Italy, but in Britain and France

and like roads they played a key role in Rome's success.

Portus is clearly an engineering marvel and I am just blown away

at the Roman's ability to build roads and infrastructure,

to dig out harbours, just to get things done.

And it's also taught me a huge amount about how the Romans

controlled their empire.

Because the Romans are famous for being soldiers but clearly

they are just as impressive as engineers.

By creating this infrastructure, by building ports,

by establishing shipping lanes and building roads,

they're shrinking their world,

they're bringing their provinces closer to Rome

and making it easier to control them.

Having finally got the satellites to deliver, it's game on.

With such a vast area to control,

Rome's military options were always going to be limited.

A whole range of tactics were needed to stay in charge.

But current thinking is incomplete.

Sarah's challenge now is to fill in the gaps...

..right across the Empire.

'Arabia.

'Exotic.

'Sophisticated.

'A land of adventure...

'..and opportunity.

We've travelled over 1,000 miles across the Mediterranean,

to what was the easternmost fringe of the Roman Empire,

modern-day Jordan.

Coming here is a chance to see something completely different

to the killing fields of northern Europe.

Amazingly, the Romans seem to have conquered this entire territory,

then kept it under control,

apparently without spilling a single drop of blood.

Our mission is to find out how.

Right, Dan. I want to show you something.

Let me pinch in a little bit here. Can you see that there?

-Yeah, rectangular?

-Yeah, it looks like a building.

And you think that might be Roman?

Hopefully. Hopefully, it's Roman. That's what it looks like.

And it's never been discovered before?

As far as I know, it's a completely new structure.

Sarah, there is no end to your skills. That's very cool.

I'm pretty excited about it.

Sarah thinks she's made a brand-new discovery

on the outskirts of an ancient city.

But not just any old city.

'It is one of the most beautiful places on Earth...

'..the rose-pink city of Petra.'

I always wondered whether I'd come back here.

It's a very special place for me, cos I came here with my mum and dad

when I was a kid and our whole family walked through

that narrow dry river bed and we came out, I always remember it,

we came out into that open space

and we saw the incredible building in front of us.

I think that was really the moment

that really fired my interest in history.

Seeing these vast buildings hacked into the living rock.

It's like nowhere else on earth.

But enough reminiscing.

It's time to get back on the job.

And look at why Rome was interested in these lands in the first place.

Before the Roman takeover, Petra was the capital city

of the great kingdom of Nabataea...

..whose merchants had grown rich

controlling the important trade routes from the Red Sea to Syria.

It was a massive money spinner and Rome wanted a slice of the action -

in the form of taxes and tariffs.

But whereas invasion would normally lead to resistance,

here the opposite seems to have happened.

And I think the reason may be partly cultural.

Unlike the so-called barbarians, the people here in the Middle East

were literate and sophisticated.

They lived in cities for a start.

The sort of people the Romans felt they could negotiate with.

To find out what the Romans had to trade,

we are off to visit their fort at Azraq

which guarded the trade routes.

'Strong, impregnable and built of solid stone.'

OK, you leave these doors to me, Sarah. Here we go.

'Including the doors.'

-Can I have a hand?

-You need Cambridge woman, Dan.

HE GROANS WITH EFFORT

SHE LAUGHS

HE SIGHS WITH RELIEF

That is ridiculous.

Before the Romans arrived here,

the Middle East had been the setting for conflict and instability

since the very beginning of recorded time.

This is where empires and civilisations clashed.

You got people like the Seleucids to the north,

the Judeans and the Egyptians out there to the west

and Mesopotamians to the east

and, of course, the fierce desert tribesmen to the south.

The result was constant violence.

So, when the Romans arrived, they bring peace and security.

And it doesn't even take that big a military force to achieve it.

This happened gradually following the Roman takeover.

But it looks like a guarantee of peace may have been enough

to win the locals over without waging war.

Because peace would bring prosperity.

It's a theory that archaeologist Dr Chris Tuttle believes.

But despite being one of the world's leading lights

on Roman Arabia, he has yet to find the proof.

That's because, after 2,000 years,

evidence of widespread abundance under Roman rule

is almost impossible to come by.

But with the aid of state-of-the-art satellite technology,

all that could be about to change.

I've been surveying an area in the countryside around Petra,

about ten square kilometres.

Do you see right here?

There are about 60 features that have appeared

-which show up in these red circles.

-OK. Wow.

This is really incredible. I mean, there's so much stuff out here

that you're finding in these satellite images.

Based on what I know of this area, this is probably

farmsteads, hamlets, possibly some watchtowers,

maybe these are agricultural water management systems.

All in all, really suggesting a landscape of abundance,

not just inside Petra but outside as well.

Yeah, but what really interested me, Chris,

was this particular feature right there.

Let me zoom in a little bit more. You can see it pretty clearly here.

Wow, that's very large.

So this, out of all the features that appeared on the satellite imagery,

really kind of grabbed me the most.

Well, we should go take a look at it and see if it

has occupation during the Roman period.

-I'd like to see it.

-All right, let's go.

We're heading into a countryside that appears barren

to look for evidence that it flourished under the Romans.

It's a confusing landscape of sand and rubble.

But with the aid of satellite technology,

Sarah can take us straight to the spot.

Wow, you guys. This is a really big site and very exciting.

So what do you think it might have been?

Like a domestic or a fort or something like that?

Well, actually it's most likely related to farming.

And it's very big so we're dealing with something like a...

It's a big farming system, this is probably the farm estate house.

What do you think the time period might be for this site?

Hard to tell without finding something to see if we can date it.

-Why don't we go take a look?

-Let's go.

OK, what are we looking for, archaeologists?

Pottery!

-DAN LAUGHS

-Ah, OK.

Ever since I've started hanging out with Sarah,

I've had a crick in my neck.

She spends the whole time staring at the ground,

looking for smashed old bits of pottery,

which she then claims, like this one here,

which she claims that she can tell the date from.

I mean, you've got to be kidding me.

I think that's all they do in archaeology school

for three years is just look at old bits of pottery.

Historians, we like a bit of papyrus or a scroll!

That tells you stuff.

OK, let's take a look at what we found.

OK, a lot of stuff that we really can't tell much about.

Those are really nice.

Sorry, Dan, no. But this one we can take a look at.

Ah, Sarah, these are perfect. Excellent, excellent.

Well, we definitely have pottery here indicating that this farm

was in use during the Roman period.

But looking at the size of it, we can see that there's even

expansion that's probably taking place at this time.

From the work you're doing in Petra and from the results that are

coming up on Sarah's satellites, this area seems to be flourishing.

I couldn't agree more, I think the satellite technology

in particular is really going to help us get a better understanding

of this time period here in Petra and in its surrounding environs.

You've revealed a lot of potential sites

that will help us understand this period in history a lot more.

Rome was mainly an agricultural society -

the majority of its citizens were farmers.

And we now know that thousands of them came from here -

Arabia.

Sarah's satellites show a countryside

brimming with farmsteads, growing olives, cereals and fruit trees -

a flourishing Arabia under Roman rule.

'It helps us understand how Rome ruled without resorting to violence.

'Rome brought peace and prosperity

'and a rich people are less likely to resist.

This leg of the journey has really helped me

to get some answers to my original question.

Just how did Rome manage to rule over such a vast empire

stretching here from the deserts of Arabia

right the way across to the west coast of Britain

with actually a relatively small number of full-time

professional legionary soldiers.

I think coming here and seeing how it all worked

has made me think about cooperation.

I think the Nabateans and the Romans that occupied Petra

both realised pretty quickly

they could achieve a lot more if they cooperated. Trade flourished

because they could now export from here right across the Empire

and import goods as well.

Also, the Nabateans realised they didn't have to spend money on a

standing army any more because the Romans would look after

external security. It was all very different in northern Europe.

There the tribes that the Romans dismissed as barbarians were

less interested in trade and interacting with the Roman Empire.

They didn't want to go to the theatre. They had to be destroyed,

one after the other, with overwhelming military force.

Here in Petra, people saw the benefits of working with the Romans.

I don't think the Romans needed to send armies

through these streets keeping the Nabateans loyal.

The people here were happy to be Roman.

It's time to return to Portus,

the great lost harbour.

Because creating prosperity, with or without warfare,

would never be enough to rule an entire Empire.

There is more still to learn.

The power of mind games.

Back in her lab in Italy, Sarah has made

an astonishing and completely unexpected discovery.

So, in this particular satellite image,

you can see we're to the northeast of the Trajanic Basin.

And we're looking at fields.

You know, partially cultivated, nothing's apparent in them.

So, I looked at a satellite image from a different kind of year,

using assorted computer logarithms, and this is what I found.

-Oh, good heavens.

-Wow!

-That really is interesting.

Simon, what is that?

It looks to me like an amphitheatre.

I mean, you can see by the oval shape

and the fact that the sides are slightly squeezed

that it's an amphitheatre-shaped building.

No doubt about it at all.

What would the significance be of a possible amphitheatre located here?

Well, if it was an amphitheatre, it would be, I think, very significant.

I mean, one has to remember, first of all,

that amphitheatres are amongst the most iconic

of all Roman public buildings.

They are very large, they're very prominent,

they consist of banks of seating

arranged around the edge of the building,

focusing in upon an arena.

And they were used for a range of activities.

One has to think of public meetings

or mock sea battles or animal baiting.

But, of course, the most iconic activity of all

would have been gladiatorial combat.

The potential of this for our understanding of the port

is very significant, so, you know, well done, Sarah.

Amphitheatres were major status symbols.

And Portus may have had one.

There is only one way to tell for certain and that's to dig.

That could take months, even years.

Even simple geophysics here is not straightforward

because this land is privately owned.

But the satellite imagery is startlingly clear.

And to find out what this might mean for Portus,

there is only one place to visit.

A larger version of Sarah's find,

and the most magnificent building in the whole of Rome -

the mighty Coliseum.

50,000 people would have packed into here.

The mob - tumultuous, riotous,

capable of bringing down the government.

Control this mob, the people of Rome, and you control the city.

You control the city, then you control the Roman world.

For me, amphitheatres represent a coming together

of perfect order on the one hand...

..and terrible violence on the other.

A powerful combination which helped bind the Empire together.

Seating was strictly controlled.

The rich and powerful sat at the front.

Poor people and women, at the back.

It was a microcosm of Roman society,

brought together to watch a spectacle of extreme brutality.

But to what end?

What was going on here in the arena of the Coliseum

and in amphitheatres right across the Empire

was a giant communal celebration of conquest.

Slaves were dragged in here from defeated enemy armies

and from occupied provinces and then slaughtered

again and again and again in huge re-enactments of Roman victories.

The people watching these spectacles would have been left in no doubt

that Rome was utterly dominant.

And nowhere was it more important to assert imperial authority

than Portus, the gateway to the Empire.

It looks like close to its heart there was an amphitheatre,

the very embodiment of Roman pomp, swagger and showmanship.

'A building designed to send subliminal messages

'reverberating right across the Empire.

'Back in Portus, it's an idea Simon Keay is keen to explore.

'For him, the whole harbour worked like some gigantic piece of theatre.

'The psychological impact of its buildings

'every bit as powerful as their practical function.

'His team are busy excavating a part of the harbour

'which makes the point perfectly.'

So, Simon, what are we looking at here?

Well, we are right in the centre of the port and in front of us

we have a building that's 200 metres long and 14 metres high,

just dominating the basin as you approached it.

And is the ship-sheds of ancient Portus.

These sheds would have housed warships belonging to

a detachment of the Imperial Fleet.

So we are talking here about an absolutely gigantic building.

-This is on a huge scale.

-It is, it's on a massive scale.

One has to imagine you are in a ship coming from the Provinces

and you've never seen buildings on this scale before.

Pretty intimidating, I think.

It's built partially functionally,

large but also built to make you feel small

and that's exactly what this was intended to do.

It's amazing because you've described the port as a social phenomenon -

they've been able to bring in all the grain -

as an engineering marvel,

but there's also a psychological dimension.

The genius of it is that it's about, as you say,

it's about trade, it's about economics

but it's also about ideology and symbolism.

It's very much a case of architecture being used

as a way of trying to control people.

It's a very remarkable complex.

'And there is nothing to make the first-time visitor feel more

'insignificant than a 25-foot giant dominating the centre of the port.

There's one last thing

and that is the long-lost statue of the Emperor Trajan.

It must have been extraordinary.

Trajan was a great general, of course -

as you know, he conquered Dacia.

He also undertook military campaigns in the Middle East.

His qualities are summed up in this great statue,

which just dominates by virtue of its sheer scale.

What does that statue tell us about how he wants to be remembered?

Emperor worship was prevalent in the Roman world.

It played a very important role in the political process

and, I think, to see a statue this size,

in the context of this great harbour,

it would really have put you in your place

and be a reminder about the strength of Roman power.

You'd have felt like you were in the presence of a god.

Exactly.

'The giant statue and the ship-sheds of ancient Portus

'were designed to dazzle the senses.

'Along with Sarah's fabulous new discovery, the amphitheatre.

'Only the great lost lighthouse itself

'was a more potent symbol of Imperial power.

'And it was symbols more than fighting

'that bound the Empire together.'

Buildings like the Coliseum were

so much more than just beautiful architecture.

They are vital clues that tell us how Rome managed

to maintain its grip on its Empire.

Nowadays, people get a lot of their information through reading

newspapers or magazines or the internet.

But back in Roman times, a lot of people couldn't read and so symbols

become vitally important and that's why Rome built huge statues,

temples, triumphal arches and amphitheatres

right across its Empire.

Because they drive a simple message into the minds

of anyone who sees them,

that a civilisation that's capable of building things like this

is a force to be reckoned with.

'We've seen the majesty of Roman rule around their capital city...

'..their crushing of the barbarian horde in Europe...

'..and how they held on to power in the sophisticated east.

'Rome's vast, sprawling Empire

'covered 5 million square miles of land.

'There is only one place left to look.

'Africa.

'It's somewhere I've always wanted to come and see for myself.

'Because controlling these lands set Rome its greatest challenge of all.

'And it'll be Sarah's greatest challenge

'working out how they achieved it.

'Crack this and we'll complete the picture.

'We're flying to Tunis, in modern-day Tunisia,

'to begin our task.

'After annihilating its bitter rival, Carthage, here in 146BC,

'Rome seized a large section of the North African coastline.

'So far so good.

'It met with little resistance

'and Africa's rich, loamy soils

'could provide Rome with the one thing it craved more than anything.'

-Sarah, look what's in all these fields.

-What's that, Dan?

You've got to take your head out of that computer from time to time.

THIS is what it's all about.

You see, it's pretty green as it's early in the year.

But we've been driving through miles and miles...

of wheat.

Look at that. I mean, this whole area is so fertile,

and, of course, we're only two days journey by boat away from Portus.

So this wheat can be in Roman bread ovens in just a matter of days.

You know, even by 50BC,

this area is producing 250,000 tonnes a year.

That's more than half of Rome's annual consumption of wheat

coming from this area. I mean, this is Rome's granary.

'But as Rome grew, so did its appetite.

'By the First Century AD, it was the biggest city in the world,

'with up to a million inhabitants.

'And without enough bread to feed all those extra hungry mouths,

'there'd be rioting in the streets.

'With demand for wheat now exceeding production along the African coast,

'Rome turned its eye inland, to the central Tunisian plateau.

'Ideal for wheat production on an industrial scale.

'But there was a problem.'

That's a heck of a view, Sarah.

It's amazing just how much you can see.

-Yeah.

-It's vast.

-It's a big, big space, this.

'The plateau was nearly 17,000 square miles.

'So once the wheat was planted,

'how could Rome defend such a huge expanse of territory?

'Nomadic farmers had been using this land themselves for generations

'as summer grazing ground for their sheep and goats -

'livestock which could eat or trample a farmer's crops

'before they could be harvested.

'So to safeguard Rome's food supply,

'the pastoralists had to be stopped.

'To control their movement and keep an eye out

'for raiding parties from the desert,

'a sophisticated frontier system was constructed.

'A series of walls and ditches stretching

'from modern-day Libya all the way to Morocco.

'But how could Rome, with such a small professional army,

'possibly defend a 1,500-mile-long frontier?

'The world expert on Rome's southern frontier is Professor David Mattingly.

'He thinks he knows the secret,

'but there is one gaping hole in his theory.'

-Hey, how are you?

-Hello, good to see you.

-Yeah, good to see you.

It's good to be here in the desert.

'Sarah is hoping she can help.'

Perfect weather to find some Roman stuff.

-Hey. Nice to meet you, David.

-Lovely to see you.

Right, so, David, I wanted to show you something

spotted from the satellite imagery.

I wanted to get your opinion on what you think you're looking at.

What do you make of that?

Wow, that's wonderful. That-that looks like a Roman fort.

That's a very distinctive shape, isn't it?

Is it those round corners, is that what makes you think it's a fort?

Yes, and you know, it's got a large ditch around the outside.

You can see some central structures within it.

And then, I mean, this looks to me like quite a large settlement

right around it, almost like village around it.

How exciting is this new technology?

You're here on the ground, what does this add?

30 years ago, I came into this area with, you know, before GPS,

no satellite imagery, didn't even have air photographs.

I had some old maps and sort of 19th-century references

to the odd site.

And as I found some elements, the garrison that manned the frontier

was completely missing and I've been waiting 30 years

for the technological breakthroughs

to be able to come back and complete the story.

'But before we check it out on the ground, David wants to explain

'how the frontier system might have worked with a relatively small

'number of soldiers, acting more like border police than warriors.

'We're on our way to see something

'that doesn't appear in any tourist guide.'

-Follow me but watch your footing on this.

-Yeah, it's a good climb.

'High in the Cherb mountains of southern Tunisia,

'the Bir Umm Ali wall.'

-So how amazing is this view?

-Oh, it's incredible.

What a view, it's extraordinary.

This is a Roman frontier wall that's running down this slope

and completely closing off this mountain pass.

I like to think about this as a point of control in the landscape.

Out there, desert landscape, little vegetation, we've got oases,

there's some great salt flat areas, very desolate.

Behind us, we've got rich pasture, agricultural zone,

and what Rome was trying to do is to control the movement of people

between the desert and that cultivated zone.

The wall may have controlled but why not just keep them out altogether?

If they'd tried, they would have been fighting a perpetual war

with these desert peoples.

This way, they incorporate them into the structure

of the Roman Empire and they can achieve that

with a much greater economy of force.

This becomes a permeable frontier rather than a line at which

you repulse those desert peoples.

'The idea that the frontier was policed by Roman soldiers

'acting more like customs officials than Royal Marines

'is an interesting theory.

'But it's only a theory.

'Where the soldiers came from to man this isolated outpost

'is a question David has never been able to answer.'

Right, David, we should be getting pretty close.

I can't see anything out there on the landscape, can you?

Can you make anything out? Over.

OK, I'm looking out. I can't see anything.

Amazing empty landscape we're looking at. Over.

'According to my GPS and satellite imagery,

'we're about 500 metres away.'

There's a fork in the road here,

do you want to go right or left? We need to go...

I think we just need to continue on ahead, according to my GPS.

Sarah, do you think it's the mound over there on the right now?

'We could stop and have a look. Over.'

Copy that. Over and out.

How are we looking? You think this is it?

Yeah, I think that's definitely... That's definitely it.

'Surrounding what may have been the fort is the 2,000-year-old debris

'of a large and densely populated village.'

Look at all this pottery in front of us.

Yeah, we need some diagnostics.

Whoo-hoo!

So what can you tell from that?

Well, that's a classic early second century Roman bowl.

And that would normally, in this part of the world,

at that date, go with a military site.

So that's, I think, a pretty good confirmation of

what we're dealing with on this site is military.

Wow. This is the ditch, isn't it?

-Absolutely right.

-That's amazing! And this is the fort here.

It's exactly like the satellite photo. It's brilliant, isn't it?

Yeah, the platform of the fort just standing up here is really clear.

-Uh-oh, somebody's been digging.

-This is not good.

Looks like we've had some local treasure hunters in action.

Not good.

What? Local people just looking for coins and things like that?

Just digging holes. I guess so. Look at this, this is even bigger.

You can actually see where the JCBs came in

and dug out big chunks of dirt and deposited them on either side.

The only good thing about this from our point of view is

we can see some of the agricultural levels that this has cut through.

There's about two metres of floor level and deposits within this.

It shows just how long this site was running for.

David, I can tell you're very keen to get your trowel out.

You going to start digging straightaway?

-Well, it is very tempting.

-What are we looking at here?

What are these...this sort of this rocky area in the middle?

Well, from where I'm standing,

that's just a chaos of collapsed boulders, really.

I need, I think, some help from space.

Right, here we go. That's what I'm here for.

This stuff is so difficult to read on the ground sometimes

but the satellite images really come into their own.

Here we go, so we're standing right about there.

You can see almost exactly where we are.

OK, we can see the ditch very, very clearly.

But all that rubble in the middle, actually represents

what looks like a big square building.

What's it like for you guys? You're archaeologists.

This is the first time this site has been visited by archaeologists.

It's a previously unknown Roman site.

Well, I came here all those years ago

looking for exactly this sort of site.

Couldn't find it. Needle in a haystack in this valley at the time.

But thanks to Sarah, you know, here we are.

Well, I can tell you, David, that there's not just this one.

There's actually up to 20 others just like it in this valley.

I'm going to have to take that away and look for something.

That's amazing news. That, I mean, is really an extraordinary result.

You'll have to show me the rest of these a little later.

We have a lot of articles to write.

What does this now tell us about this part of the Roman frontier

that we perhaps didn't know before? What gaps does this fill in?

OK, let me do my sums quickly.

In a fort like this, it's quite a small fort,

so maybe there's 50, 100 soldiers here.

But that settlement round about can certainly accommodate

several hundred, maybe 1,000 people.

And if you say there's 20 of these in the valley,

we've got a very significant population in the valley here,

in the Roman period.

And what that tells us is that the frontier worked.

'Sarah's satellites are helping to show

'how the whole frontier system actually functioned.

'Troops were strategically positioned along the valley

'in a series of forts like this one,

'and used as border police to manage the movement of people across

'the frontier, rather than ban entry altogether and risk all-out war.

'And we now know that all of these forts were surrounded by

'large civilian settlements which were prosperous and stable.

'Proving once and for all that it was a system that worked.

'And worked well enough with a relatively small number of professional soldiers.

'It's a triumph. And one that calls for a celebration.

'And what could be more appropriate than an authentic Roman feast,

'cooked in the desert, by a friendly expert, Sally Grainger.

I've a few more quails here, straight off the barbie.

Always room for another quail somewhere.

How are you feeling about the high hopes we had

for those satellite results?

Have you seen it on the ground? Are you happy with what you've seen?

I'm absolutely thrilled. We think we've answered every question

and found everything there is to be found but what the satellites

are showing us is just... There's so much more left to find.

And I just think it's the most exciting time in history

to be an archaeologist.

I'll drink to that. And I'll say thank you very much, Sarah.

-Thank you, David.

-And Dan.

And thank you very much for taking us round. Thank you for the meal.

This trip to Tunisia has taught me so much about Roman frontiers,

both here in North Africa and right across the Empire.

These aren't just physical barriers, they're psychological barriers.

They dominate the landscape like no other empire has done before.

And I think that everybody who crossed those walls,

whether you go through one of the gates

or even manage to sneak over at night,

everybody who crossed those walls would know

they were now in Roman territory.

And it's also been so interesting

just how clever the Romans were as well.

They didn't just try and seal off the borders and block everybody out.

They were happy to let traffic through as long as it suited them.

They even encouraged it.

People were allowed to come through the wall,

trade was allowed to happen, but only if it suited Rome.

'We're back in Portus for one final look.

'The great lost harbour is at last making sense.

'Sarah has discovered another canal,

'bringing new insight into how

'this fabulous port complex actually worked.

'She's even found an amphitheatre,

'but the greatest prize of all has eluded her.'

Simon, there's something else I'd like to show you

that I think you'll find of great interest.

So here we have the Claudian basin with the northern and southern quays.

Based on this hypothetical location,

I've done some preliminary imagery analysis work

-that I'd like to show you.

-OK.

Yeah, that's interesting.

I mean, it's...there's very clearly something there.

I mean, I'm not entirely convinced at what it is.

'It's the culmination of Sarah's work and effort.

'The final piece of a dazzling great jigsaw.

'But maybe she's got it wrong.'

Yeah, I mean, you know, the results are, at best, ambiguous.

There's a shape perhaps but at the very least it showed me

that there could be potentially something there

and it was worthwhile doing additional processing work.

So I used a different kind of image called LIDAR.

Actually, it's the same thing we used in Romania.

We used different types of processing.

And this is what showed up!

Good heavens! Now this is a different prospect altogether!

This is really incredible.

Um...

You can see very, very clearly how that massive feature

is at an angle to the modern buildings there and also,

it's centrally located between the north and the south quays.

That's extraordinary.

And the other thing is that, it's immediately to the west

of where my Italian colleagues have been working, doing deep coring

and finding large chunks of masonry and some geophysics.

Um, but could I ask how big that is?

It's about 140 metres long, and about 40 metres wide.

Dare I say it, but this is the platform

of the long-lost lighthouse of Portus.

I can't see what else it could possibly be.

Simon, just how exciting is that?

I mean, it would be pretty hard to overestimate the significance

of finding this monument.

I mean, people have been looking for it for hundreds of years.

The lighthouse of Portus

was one of the great monuments of the Roman world.

Commemorated on coins, inscriptions and images all over the Empire.

It really represents the ultimate symbol of Rome's political

and military domination of the Mediterranean.

And indeed, given where the Mediterranean is

in the Roman Empire, the Empire as a whole.

'Imagine you're on a ship

'approaching the great harbour of Rome at night.

'The sky would have been dark in antiquity...

'..and the first thing you would have seen is a light,

'floating in the sky.

'It's like nothing you've ever seen before.

'An incomprehensible force, sucking everything in.

'The people...

'..the grain...

'..the slaves...

'..everything.

'To visit the probable location of the lighthouse involves a short trek

'across broken waste ground on the edge of Fiumicino airport.

'But there is one more surprise in store.'

OK, now, it's just over here, just there.

Hang on a second.

Are you telling me we've come on this entire journey

to find the ultimate symbol of Rome and it's in a scrap yard?

Well, let's have a look.

-Ah, now, Sarah.

-Yeah.

-The feature that you found...

-Right.

..the platform of what we thought was the lighthouse,

it was a 140 metres long, 37 metres wide.

So I calculate that the base of the lighthouse

would have been 30 metres wide,

which means that it would have stood

110 metres high and would have been right over there.

When we set out to use satellite technology to map the Roman Empire,

I genuinely thought that it was a completely crazy thing to do!

What I've come to realise is that my first real love

has and, I think, always will be finding things.

Part of me is relieved it's over.

Just because of all the challenges we've had

and everything we've been through.

But part of me kind of wonders what's next.

It's been a massive privilege watching Sarah work on this trip.

I'm just so excited that it seems like she's discovered

the site of Rome's lost lighthouse.

The symbol of their domination. And I've learnt a lot on this trip

about what underpinned Rome's domination.

Yes, Rome was a military power

but she realised that wars are expensive

and they create a backlash, they almost inflame opposition.

So Rome was also a psychological empire.

Rome overawed people, Rome impressed people,

Rome won respect by creating prosperity and security.

So the situation is that

people actually started wanting to be part of Rome's empire.

They started collecting their own tax.

They even started policing themselves.

Now, that's clever.

And that's what underpins Rome's greatness.