0:00:05 > 0:00:07This is our home.
0:00:11 > 0:00:15From up here, it looks the same as it has done for thousands of years.
0:00:17 > 0:00:22But get a bit closer and you can see we've made a few changes.
0:00:22 > 0:00:26'We're redesigning our world.'
0:00:26 > 0:00:28Three, two, one...
0:00:28 > 0:00:29Whoa!
0:00:29 > 0:00:31'Wherever you look...'
0:00:31 > 0:00:34Just don't, whatever you do, look down.
0:00:34 > 0:00:37'..you'll see the scale of this supersized transformation.'
0:00:39 > 0:00:44Our generation is changing the face of the planet as never before.
0:00:44 > 0:00:46I'm Dallas Campbell,
0:00:46 > 0:00:50and in this series I'll show you how we're shaping the modern world.
0:00:51 > 0:00:54We're building faster than ever,
0:00:54 > 0:00:58transforming whole landscapes in the blink of an eye.
0:01:01 > 0:01:05I've got DIY projects in my house that have taken longer than
0:01:05 > 0:01:07it's taken Shanghai to build an entire city.
0:01:09 > 0:01:10We're opening up the earth...
0:01:11 > 0:01:17..and conquering the sky, making it a place we can call home.
0:01:17 > 0:01:19BUSTLING VOICES
0:01:19 > 0:01:22- Do you get nervous at all?- Yes. - Get a little bit scared?- Yeah.
0:01:22 > 0:01:27I'll join the people who'll make the impossible, possible.
0:01:27 > 0:01:30This is clearly one of the most dangerous jobs in the world.
0:01:31 > 0:01:34I can't believe someone's actually thrown away a horse!
0:01:34 > 0:01:37That's the kind of stuff you find in the sewage.
0:01:37 > 0:01:39- Thank you very much.- You're my hero!
0:01:39 > 0:01:43Our world is becoming a man-made world.
0:02:11 > 0:02:12HE EXHALES DEEPLY
0:02:15 > 0:02:17This is it.
0:02:28 > 0:02:31This is as high as it's possible to climb
0:02:31 > 0:02:35on any man-made structure on the planet.
0:02:36 > 0:02:41I'm over 800 metres high. That's more than half a mile above Dubai.
0:02:41 > 0:02:44And this is the world's tallest building.
0:02:48 > 0:02:53A building like this would have been inconceivable a generation ago.
0:02:53 > 0:02:56But it's testament to what we can do now.
0:03:00 > 0:03:04Today, we build man-made mountain ranges
0:03:04 > 0:03:06stretching as far as the eye can see.
0:03:12 > 0:03:16But the story of how we scaled these heights started a long time ago...
0:03:16 > 0:03:19- CAT MEOWS - ..and right on our doorstep.
0:03:19 > 0:03:21- MAN RINGS BICYCLE BELL - Morning, vicar!
0:03:23 > 0:03:27For thousands of years we've had a passion to build high.
0:03:27 > 0:03:32In fact, Britain itself was once home to the tallest building in the world.
0:03:35 > 0:03:37In the Middle Ages,
0:03:37 > 0:03:41Lincoln Cathedral became the tallest building the world had ever seen,
0:03:41 > 0:03:44breaking the record that Egypt's Great Pyramid had held
0:03:44 > 0:03:46for almost 4,000 years.
0:03:47 > 0:03:51But if you think about it, the pyramid is almost solid stone.
0:03:51 > 0:03:55It was designed as a mausoleum for one person.
0:03:55 > 0:03:57This place, on the other hand,
0:03:57 > 0:04:00was designed for thousands of people to congregate.
0:04:02 > 0:04:05To build so high, the architects of Lincoln had to make
0:04:05 > 0:04:08a major construction breakthrough.
0:04:10 > 0:04:13If you want to build a building that's high
0:04:13 > 0:04:16and has a huge internal space, a space that people can use,
0:04:16 > 0:04:19a space that people can actually come together,
0:04:19 > 0:04:24then you really need to rethink your engineering techniques.
0:04:27 > 0:04:31The medieval builders had to come to terms with the forces of gravity.
0:04:31 > 0:04:32HE PANTS
0:04:32 > 0:04:34And to see how they did it, so do I.
0:04:53 > 0:04:56Oh, it's beautiful. Wow.
0:04:58 > 0:05:01The architects stripped as much stone from the structure
0:05:01 > 0:05:04as they dared, leaving just enough to keep it standing.
0:05:06 > 0:05:10If you just think about the physical forces
0:05:10 > 0:05:13that are at play on this building,
0:05:13 > 0:05:15all these huge bits of structure leaning against each other,
0:05:15 > 0:05:18creating this perfect balance.
0:05:20 > 0:05:23And you can see from here how it all fits together.
0:05:25 > 0:05:31A network of hundreds of arches, ribbed vaults and columns keep this building standing.
0:05:34 > 0:05:38They're like the cathedral's stone skeleton.
0:05:40 > 0:05:44The ribbed vaults help spread the immense weight of all the stone.
0:05:44 > 0:05:49The pointed arches channel the load down through the columns.
0:05:55 > 0:05:57To give the cathedral its height,
0:05:57 > 0:06:02an enormous stone tower is supported on just four great pillars.
0:06:07 > 0:06:11Nearly 700 years later, this vast building remains rock solid.
0:06:15 > 0:06:19But to be the world's tallest building,
0:06:19 > 0:06:22the medieval cathedral was once even higher.
0:06:23 > 0:06:30The current height of the cathedral is 80 metres, and it is magnificent.
0:06:30 > 0:06:32But what's even more spectacular is what you can't see,
0:06:32 > 0:06:36because actually, back in the day, it used to be a lot taller.
0:06:36 > 0:06:39Building high back then was about making a connection with
0:06:39 > 0:06:43the heavens, getting closer to God, so they just kept on going.
0:06:48 > 0:06:53Three enormous spires were built on top of the cathedral's towers.
0:06:54 > 0:06:57The largest, standing at 80 metres high,
0:06:57 > 0:07:00doubled the height of the building.
0:07:04 > 0:07:09The spires stood over two centuries before collapsing in a storm.
0:07:09 > 0:07:15But with them, Lincoln Cathedral was 14 metres taller than the Great Pyramid.
0:07:17 > 0:07:19To build higher than that
0:07:19 > 0:07:24required a revolutionary new building material - steel.
0:07:26 > 0:07:29Inspired by the engineering of the Industrial Revolution,
0:07:29 > 0:07:33the Eiffel Tower is almost twice the height of Lincoln Cathedral.
0:07:38 > 0:07:44In 1930, New York's Chrysler Building was the first "world's tallest" to use a steel skeleton.
0:07:47 > 0:07:51And just one year later, the mighty Empire State Building
0:07:51 > 0:07:54used the new construction method to go even higher.
0:08:02 > 0:08:05The next major breakthrough came in 1972
0:08:05 > 0:08:09with New York's sleek and very tall World Trade Centre.
0:08:11 > 0:08:16And soon after, Chicago's even taller Sears Tower.
0:08:17 > 0:08:23Glass walls fixed to a completely steel structure made this building much lighter.
0:08:26 > 0:08:32Later, the Petronas Towers in Kuala Lumpur used steel and glass over an outside frame of concrete
0:08:32 > 0:08:36which was built around a reinforced central concrete core.
0:08:36 > 0:08:40This provided the strength and the shape.
0:08:40 > 0:08:44Skyscrapers no longer needed to be box-like.
0:08:45 > 0:08:47They had become works of art.
0:08:50 > 0:08:54Taipei 101 was the first building to reach half a kilometre high.
0:09:01 > 0:09:04It was hard to imagine going any higher.
0:09:25 > 0:09:27These are the deserts of Dubai.
0:09:29 > 0:09:33It's in this dry and windy landscape that the world's first mega-tower has risen.
0:09:36 > 0:09:38And it's rewritten the record books.
0:09:41 > 0:09:45I'm standing in a shadow that's being cast by a structure
0:09:45 > 0:09:47with a unique claim to fame.
0:09:47 > 0:09:50It's about a mile-and-a-half or so in that direction
0:09:50 > 0:09:53and over half a mile in that direction.
0:09:53 > 0:10:00And at 829 metres, it dwarfs every other building on the planet.
0:10:14 > 0:10:16Look at it.
0:10:16 > 0:10:20It is ridiculous! That is off the chart.
0:10:21 > 0:10:24The engineers had no blueprint to copy
0:10:24 > 0:10:28when building the world's first mega-tower.
0:10:29 > 0:10:34What they came up with wasn't always as hi-tech as you might imagine.
0:10:37 > 0:10:40It looks so fragile and elegant, but if you take away all the glass,
0:10:40 > 0:10:43you can see it's actually held up by good, old-fashioned brute force.
0:10:43 > 0:10:48330,000 cubic metres of concrete.
0:10:56 > 0:11:01The Burj Khalifa has a frame made entirely of reinforced concrete.
0:11:03 > 0:11:06During its construction, liquid concrete was packed in ice
0:11:06 > 0:11:08to stop it setting in the desert heat,
0:11:08 > 0:11:12and then pumped 600 metres up.
0:11:14 > 0:11:17That took a pressure of a massive 200 atmospheres.
0:11:21 > 0:11:24Its final height advanced the "world's tallest" record
0:11:24 > 0:11:27by a staggering 320 metres.
0:11:27 > 0:11:30That's equivalent to an extra Eiffel Tower.
0:11:36 > 0:11:38Brute force raised the tower,
0:11:38 > 0:11:41but keeping it standing isn't about strength alone.
0:11:41 > 0:11:43It's also about clever aerodynamics.
0:11:43 > 0:11:47- Welcome to the Burj Khalifa. - Pleasure, thank you for having me. - Please follow me.- Thank you.
0:11:50 > 0:11:53To understand this for myself,
0:11:53 > 0:11:56I'm heading to a place few people are ever allowed to go.
0:12:01 > 0:12:05- Dallas, floor 160. - Thank you very much.
0:12:21 > 0:12:22I'm really nervous.
0:12:23 > 0:12:27- Dallas, do you want to come over? - Yeah, I'm coming.
0:12:27 > 0:12:29- OK, Dallas.- Yep.
0:12:29 > 0:12:32Just step in and I'll check you out.
0:12:32 > 0:12:35I was secretly hoping that it was going to be too windy today
0:12:35 > 0:12:38and it would all be cancelled and we could all just go home.
0:12:38 > 0:12:40Somehow the windows would just clean themselves.
0:12:40 > 0:12:42Unfortunately for you, no.
0:12:42 > 0:12:45- I'm absolutely terrified. I've never been this scared in my life.- Really?
0:12:45 > 0:12:48Well, you know, it's pretty high up here.
0:12:48 > 0:12:51DALLAS EXHALES DEEPLY
0:12:53 > 0:12:56- Good. It'll be fine. - Yeah, that's good.
0:12:56 > 0:12:58The leg ones - don't want to be too tight?
0:12:58 > 0:13:01Not too tight, so you're comfortable. Right, one more, round here. OK.
0:13:01 > 0:13:06- And you are ready to rock. Good to go.- Let's go to work.- OK.
0:13:06 > 0:13:07After you.
0:13:08 > 0:13:11- This is Xiao Lau.- Hello.
0:13:11 > 0:13:14- Good to meet you.- Barry Hannah. - Nice to meet you.
0:13:14 > 0:13:17- This is Davie.- Davie, how do you do? Nice to meet you.
0:13:17 > 0:13:19- This is Shri Krishna. - Good to meet you.
0:13:19 > 0:13:21I'm going to try and not let you down.
0:13:29 > 0:13:31Today, I'm going to join the team whose job it is
0:13:31 > 0:13:36to clean the outside of the world's highest windows.
0:13:51 > 0:13:54Just pull a little slack through.
0:13:54 > 0:13:57Just pull up on this one.
0:14:00 > 0:14:04A little bit more. OK, now lock the handle off.
0:14:04 > 0:14:06Yeah, yeah. >
0:14:06 > 0:14:09OK. OK, just lean back, just lean back.
0:14:09 > 0:14:12You're OK, you can't go nowhere.
0:14:15 > 0:14:19- I need the bucket.- Yeah, hang on a second. Take this...
0:14:21 > 0:14:23Dry mouth.
0:14:23 > 0:14:25Do you get nervous at all?
0:14:25 > 0:14:29- Yes.- Get a little bit scared?- Yeah. - I haven't looked down yet.
0:14:30 > 0:14:33Now I've looked down!
0:14:34 > 0:14:39It's almost inconceivable how high these windows are.
0:14:39 > 0:14:42I'm 60 metres above the next platform below,
0:14:42 > 0:14:46which is, in itself, 600 metres above the ground -
0:14:46 > 0:14:49higher than the previous world's tallest building.
0:14:57 > 0:14:59At this height, if I dropped anything,
0:14:59 > 0:15:01it could do serious damage.
0:15:11 > 0:15:15Building high, there's a load of factors you've got to take into consideration.
0:15:15 > 0:15:18One of them is gravity, which I'm feeling right now.
0:15:18 > 0:15:21But the thing about gravity is it's very predictable.
0:15:21 > 0:15:23It's a force that's going one way.
0:15:23 > 0:15:25The thing you've really got to worry about is wind,
0:15:25 > 0:15:29because by its very nature it's unpredictable, it swirls around
0:15:29 > 0:15:33and it can affect the building - as well as window cleaners.
0:15:36 > 0:15:39Surprisingly, very tall buildings aren't in danger of
0:15:39 > 0:15:42being blown over, but of being sucked over.
0:15:44 > 0:15:49As wind hits them, it can form small whirlwinds, called vortices.
0:15:49 > 0:15:54This swirling air can create low-pressure areas that tug at the building.
0:15:54 > 0:15:57And if enough of them combine up the tall straight sides,
0:15:57 > 0:16:01they could make the tower rock from side to side.
0:16:02 > 0:16:05So why doesn't this happen to the Burj Khalifa?
0:16:05 > 0:16:09Well, it's taken some careful aerodynamic design.
0:16:10 > 0:16:13By stepping the building in as it rises
0:16:13 > 0:16:17and introducing angles and curves, the Burj Khalifa breaks up
0:16:17 > 0:16:21the desert wind, preventing the vortices from combining dangerously.
0:16:24 > 0:16:27The designers call it "confusing the wind",
0:16:27 > 0:16:30and they reckon it's the only way to build this high.
0:16:33 > 0:16:36It strikes me, being out here, that even though we are in such
0:16:36 > 0:16:42a technically advanced building, in order to keep it nice and clean,
0:16:42 > 0:16:47you still can't beat a man with a squeegee and a bucket.
0:16:55 > 0:16:58It takes three months to clean all 24,000 windows,
0:16:58 > 0:17:04and when they've finished, the team has to start all over again.
0:17:04 > 0:17:07If you are going to build a building that's truly iconic,
0:17:07 > 0:17:08you've got to make it look nice.
0:17:08 > 0:17:12- And keep it looking nice!- And keep it looking nice, exactly, yeah.
0:17:28 > 0:17:32Keep going, you're all right. Keep going. Lovely.
0:17:35 > 0:17:39Wow, that was intense! I don't know how those guys do it every day.
0:17:39 > 0:17:41EXHALES DEEPLY
0:17:41 > 0:17:44That was intense. But good.
0:17:48 > 0:17:53The tallest structure on the planet shows the extent of our ambition.
0:17:55 > 0:17:58The small fishing village of Dubai has been transformed
0:17:58 > 0:18:02into a metropolis of over two million people.
0:18:04 > 0:18:06In just 30 years,
0:18:06 > 0:18:10over 150 skyscrapers have risen from the sands.
0:18:15 > 0:18:18And the mighty Burj Khalifa acts like a beacon,
0:18:18 > 0:18:23drawing the world's attention to this city in the desert.
0:18:23 > 0:18:26It would have been impossible to achieve a generation ago.
0:18:47 > 0:18:48Hey, come on!
0:18:48 > 0:18:50Get outta here!
0:18:51 > 0:18:55The epic scale of our redesign of the Earth
0:18:55 > 0:18:58is most obvious in the world's cities.
0:19:03 > 0:19:06Almost as many people live in urban areas today
0:19:06 > 0:19:10as existed on the entire planet in 1970.
0:19:14 > 0:19:18And in 2008, we reached an important tipping point.
0:19:18 > 0:19:21For the first time in human history,
0:19:21 > 0:19:25more than half of us live in towns and cities.
0:19:25 > 0:19:29We've paved over a million-and-a-half square miles of the Earth's surface.
0:19:29 > 0:19:32Now, to really understand what that means,
0:19:32 > 0:19:37try and imagine all the cities brought together in one place.
0:19:46 > 0:19:51A bristling forest of skyscrapers would stretch further than the eye could see.
0:19:56 > 0:19:58London, neighbours with New York.
0:20:02 > 0:20:04Paris alongside Tokyo.
0:20:08 > 0:20:11One vast, sprawling super-city.
0:20:23 > 0:20:26But the most amazing thing is if you were to pull together
0:20:26 > 0:20:30all of the world's urban areas side by side, then that monster
0:20:30 > 0:20:35metropolis would only cover about 1% of the surface of the planet.
0:20:37 > 0:20:40In other words, over half of us live together in a space that would
0:20:40 > 0:20:45fit comfortably onto an island just half the size of Australia,
0:20:45 > 0:20:50or 187 times the size of Wales. That's the country, not the mammal.
0:20:58 > 0:21:01When so many of us choose to live in cities,
0:21:01 > 0:21:04the challenge is to cram everyone in.
0:21:05 > 0:21:08Hong Kong is now one of the most densely populated cities
0:21:08 > 0:21:10in the world.
0:21:19 > 0:21:22But though it looks like a city of the future,
0:21:22 > 0:21:25much of Hong Kong has actually been built
0:21:25 > 0:21:29using a scaffolding method from the past.
0:21:33 > 0:21:36And this is the wonder material, just good old bamboo.
0:21:36 > 0:21:39They've been using this for thousands of years.
0:21:39 > 0:21:44As a scaffolding technique, if it ain't broke, why fix it?
0:21:44 > 0:21:45Hi, Clement, how are you today?
0:21:45 > 0:21:47Good, how are you?
0:21:47 > 0:21:49Will you be able to get all this up in a day?
0:21:49 > 0:21:51- Yeah.- Seriously? - Yeah, yeah, yeah.
0:21:51 > 0:21:53It's pretty high, how many floors is that?
0:21:53 > 0:21:55It's 13 floors.
0:21:55 > 0:21:58So why bamboo, why not steel? What's good about bamboo?
0:21:58 > 0:22:01Compared with the metal scaffolding it's much cheaper,
0:22:01 > 0:22:02and it's easy to install.
0:22:02 > 0:22:05And presumably, as well, I mean, we were watching them,
0:22:05 > 0:22:07- you can cut it to size, you just chop a bit off?- Right, yeah.
0:22:07 > 0:22:09If it's very windy,
0:22:09 > 0:22:13if there's, like, a typhoon, do you leave the scaffolding up?
0:22:13 > 0:22:17- We still leave it.- It's fine in high winds?- It's fine.
0:22:17 > 0:22:19Does it take a lot of training?
0:22:19 > 0:22:21- Over ten years. - Over ten years!
0:22:21 > 0:22:24I'd quite like to have a go and just see how difficult it is.
0:22:34 > 0:22:38Bamboo's hollow stem and tough fibres make it light and strong,
0:22:38 > 0:22:41and the joints in each pole give it the flexibility it needs
0:22:41 > 0:22:44to cope with extreme weather.
0:22:47 > 0:22:51The professionals can construct over 100 metres in a day.
0:22:53 > 0:22:56I like to think I've contributed my little bit.
0:22:59 > 0:23:01- Look at that! - Yeah. good.
0:23:05 > 0:23:10Every year, the demand for living space in Hong Kong increases.
0:23:10 > 0:23:13And as more homes are squeezed in, buildings keep getting higher.
0:23:19 > 0:23:22Ap Lei Chau is one of the densest residential areas of the city.
0:23:25 > 0:23:29Yin Yin Tong's family lives over 70 metres up.
0:23:31 > 0:23:33Her children only know a life in the sky.
0:23:37 > 0:23:39- In you go.- OK.
0:23:39 > 0:23:42- Right, what floor are we going to?- The 25th floor.
0:23:42 > 0:23:45- 25.- 25.- It's all about elevators, Hong Kong.
0:23:45 > 0:23:48Yes, up and down, up and down, down and up.
0:23:50 > 0:23:53Yin Yin moved here from England, in 2004.
0:23:53 > 0:23:57- So you've left Brighton for your new life in Hong Kong.- Yes.
0:23:57 > 0:24:01And you arrive at your front door in your brand new flat.
0:24:01 > 0:24:05- What do you think? - Blimey, this is small.
0:24:08 > 0:24:10It's small, but is this a sort of normal...
0:24:10 > 0:24:13I mean, would this be considered small in Hong Kong standards?
0:24:13 > 0:24:15No, this would be considered quite big.
0:24:15 > 0:24:18- It's a pretty spectacular view, isn't it?- Yeah, it is.
0:24:18 > 0:24:22What about playing, I mean for kids, obviously, they need to run around?
0:24:22 > 0:24:25There's a park downstairs.
0:24:25 > 0:24:28- Even that's actually raised up, as well.- Yeah, it is raised.
0:24:28 > 0:24:30Everything's slightly raised up.
0:24:30 > 0:24:33Yeah, even the netball court is, like, raised up from the ground,
0:24:33 > 0:24:37- so nothing is completely on ground level.- Yeah.
0:24:37 > 0:24:42This is worlds away from what Yin Yin grew up with back in the UK.
0:24:42 > 0:24:45How is it different, living in a high-rise area?
0:24:45 > 0:24:51Well, just everything is geared upwards, basically. You adapt to it.
0:24:51 > 0:24:55Most people here live like this, so you have to get used to it.
0:24:56 > 0:24:58What kind of mushrooms are these?
0:24:58 > 0:25:01These are Korean mushrooms, Korean mushrooms.
0:25:01 > 0:25:05You're not supposed to eat them.
0:25:05 > 0:25:06You can eat a raw mushroom!
0:25:08 > 0:25:10Not Korean ones!
0:25:16 > 0:25:18Over 1,000 people live in each of these blocks,
0:25:18 > 0:25:22and there are at least 20 of them in this one estate.
0:25:22 > 0:25:26So more than 20,000 people live within a half mile radius,
0:25:26 > 0:25:29stacked one on top of the other.
0:25:33 > 0:25:36Hong Kong has embraced high-rise living so successfully, nearly
0:25:36 > 0:25:40three million people make their home above the 14th floor.
0:25:42 > 0:25:45That's more than the population of Chicago,
0:25:45 > 0:25:47America's third-largest city.
0:25:55 > 0:25:57The modern city is extraordinary.
0:25:57 > 0:25:59It might just be our greatest invention.
0:25:59 > 0:26:02I mean just look around here for example, try and imagine,
0:26:02 > 0:26:05try and visualize what all those people living together
0:26:05 > 0:26:07actually looks like.
0:26:08 > 0:26:11MUSIC: "Warm In The Winter by Glass Candy
0:26:11 > 0:26:15# Love is in the air, oh
0:26:17 > 0:26:23# Love is in the air, yeah
0:26:25 > 0:26:28# We're warm in the winter
0:26:29 > 0:26:31# Sunny on the inside
0:26:33 > 0:26:35# More warm in the winter
0:26:37 > 0:26:38# Sunny on the inside
0:26:40 > 0:26:42# Woo! #
0:26:56 > 0:26:59It's not just Hong Kong.
0:26:59 > 0:27:03Across the planet, hundreds of millions of us
0:27:03 > 0:27:06are squeezing into cities that have risen into the sky.
0:27:15 > 0:27:19In a single generation, the urban world has exploded in size.
0:27:21 > 0:27:24In 1970, just two cities on the planet
0:27:24 > 0:27:26had a population of more than ten million.
0:27:29 > 0:27:30Now there are 21.
0:27:33 > 0:27:37Our future is staked on the success of these vast urban areas.
0:27:39 > 0:27:42And to keep a mega-metropolis running smoothly
0:27:42 > 0:27:44demands some mega engineering.
0:28:01 > 0:28:07This city has a major problem staying healthy.
0:28:10 > 0:28:14The reason? It's been built in entirely the wrong place.
0:28:19 > 0:28:22So over there, in that direction, just through the smog,
0:28:22 > 0:28:24you've got a chain of active volcanoes.
0:28:24 > 0:28:28That way, you're right by one of the world's earthquake hotspots.
0:28:28 > 0:28:31So, all in all, you'd think it's not really an ideal location
0:28:31 > 0:28:34for a city of over 20 million people.
0:28:34 > 0:28:37And if that wasn't bad enough, there's something else.
0:28:40 > 0:28:44Mexico City is built in the crater of an enormous volcano.
0:28:44 > 0:28:47And it's on the move. Downwards.
0:28:50 > 0:28:54Just to give you an idea of the extent of the problem, Venice,
0:28:54 > 0:28:57which I suppose is the city we most associate with sinking,
0:28:57 > 0:29:01is dropping around about seven inches over the last century,
0:29:01 > 0:29:02so, you know, the height of a kerb.
0:29:02 > 0:29:08Mexico City, by contrast, has dropped around 30 feet,
0:29:08 > 0:29:10so about the height of this entire building.
0:29:10 > 0:29:12And you can kind of see it everywhere you go in Mexico City.
0:29:12 > 0:29:15The whole place is, sort of, undulating.
0:29:15 > 0:29:16Nowhere is really level.
0:29:16 > 0:29:19In fact, you might be able to see just over there,
0:29:19 > 0:29:21where that car's coming, the road is kind of bent and buckled.
0:29:21 > 0:29:24The entire city is just slowly sinking downwards.
0:29:29 > 0:29:32The subsidence is bad enough at street level.
0:29:32 > 0:29:36But Mexico City's problems are even worse under the ground.
0:29:36 > 0:29:40The plumbing that keeps the city healthy is failing fast.
0:29:48 > 0:29:49120/80.
0:29:49 > 0:29:51Esta muy bien.
0:29:52 > 0:29:53As the ground sinks,
0:29:53 > 0:29:57it reverses the downward gradient of the sewage system,
0:29:57 > 0:30:00so instead of all the raw sewage flowing away from the city,
0:30:00 > 0:30:04as is customary, it actually starts to flow back towards the city.
0:30:04 > 0:30:06And obviously, you know, if nothing's done about that,
0:30:06 > 0:30:09it means Mexico City will end up drowning in its own filth.
0:30:11 > 0:30:15Engineers have begun work on a new super-sewer.
0:30:15 > 0:30:20But until it's ready, professional diver Julio
0:30:20 > 0:30:22has Mexico's most unenviable job.
0:30:26 > 0:30:29And today, the most nervous apprentice.
0:30:31 > 0:30:35Mexico City's sewers get blocked up so regularly,
0:30:35 > 0:30:39Julio and his team are forced to dive into the raw sewage
0:30:39 > 0:30:42to unblock the pipes by hand.
0:30:45 > 0:30:48If you came into contact with raw sewage, how dangerous is that?
0:30:48 > 0:30:50What kinds of diseases could you get?
0:31:06 > 0:31:09OK, well, that doesn't sound too bad. That sounds all right.
0:31:14 > 0:31:15Hey!
0:31:15 > 0:31:19'My job today is to help Julio maintain one of the massive pumps
0:31:19 > 0:31:22'that keeps the sewage moving.'
0:31:23 > 0:31:27When you look at the surface of it, I'd just assumed that was the floor.
0:31:27 > 0:31:30I'd assumed people had just dropped rubbish there.
0:31:30 > 0:31:32And then I realized that's actually the surface of the water.
0:31:32 > 0:31:37It's truly disgusting. And the smell is so bad. It's indescribable!
0:31:39 > 0:31:42Several pumping stations, like this one,
0:31:42 > 0:31:46force Mexico City's sewage uphill and out of the city.
0:31:47 > 0:31:51But the huge underwater pumps regularly become blocked with
0:31:51 > 0:31:53rubbish dumped into the sewers.
0:31:55 > 0:31:57What exactly are we going to be diving into today?
0:32:03 > 0:32:05- Aguas negras?- Aguas negras.
0:32:05 > 0:32:07- Black water.- Yes.- Why?
0:32:07 > 0:32:10As if I need to ask why it's called black water!
0:32:22 > 0:32:25Mexico City, unlike, say, London,
0:32:25 > 0:32:29dumps all of its liquid waste into a single sewer,
0:32:29 > 0:32:33making this some of the most toxic sewage on the entire planet.
0:32:35 > 0:32:38I mean, this is clearly one of the most dangerous jobs in the world.
0:32:38 > 0:32:42- How many divers in your team? - Dos, dos buzos.
0:32:42 > 0:32:45- There's two divers for the whole of Mexico?- Yes.
0:32:45 > 0:32:46- That's it?- Yes.
0:32:49 > 0:32:53I shouldn't be surprised that few people want a job this perilous.
0:32:55 > 0:32:58One of Julio's colleagues was drowned when he was swept away
0:32:58 > 0:33:01by an unexpected surge of wastewater.
0:33:03 > 0:33:05- And this is definitely closed?- Si.
0:33:05 > 0:33:08It's closed? Let's just keep it closed, we'll keep it closed?
0:33:08 > 0:33:11- Esta cerrado.- It's closed? It's done? OK, cool.
0:33:11 > 0:33:13All right, I'm ... scared now.
0:33:16 > 0:33:18- Thank you.- OK?
0:33:18 > 0:33:21This gaffer tape, this is OK on the suit?
0:33:21 > 0:33:23- No problem.- No problem?- OK.- OK.
0:33:31 > 0:33:33Dallas, are you OK?
0:33:33 > 0:33:34I'm good, I'm fine.
0:33:34 > 0:33:36'You are ready to go.'
0:33:48 > 0:33:51Oh, my God, this is scary.
0:33:58 > 0:33:59Good luck!
0:34:09 > 0:34:11OK, we're just about at the surface of the water.
0:34:15 > 0:34:17OK, here we go!
0:34:23 > 0:34:25My God, it's completely black.
0:34:28 > 0:34:31Pitch black, but hopefully, with a torch you can see
0:34:31 > 0:34:33the horrors that are beneath here.
0:34:36 > 0:34:40Just bits of food floating about, God knows what.
0:34:42 > 0:34:44You know, when you pull the chain
0:34:44 > 0:34:46you're not really expecting to see it again.
0:34:49 > 0:34:52Ah, look at that, it's just disgusting.
0:34:54 > 0:34:56OK, so Julio's going to go and fix the pump.
0:34:58 > 0:35:00And we're going to be his side-buddy.
0:35:00 > 0:35:03I've got the other end of the rope, and I'm going to hold the rope.
0:35:04 > 0:35:09I can just feel, just poo beneath my feet.
0:35:09 > 0:35:1520 million people's worth of poo beneath me.
0:35:17 > 0:35:19What is that?
0:35:20 > 0:35:24Oh, my God, look at this, look at this.
0:35:26 > 0:35:28This is the kind of stuff you find in the sewage.
0:35:28 > 0:35:32I can't believe someone's actually thrown away a horse.
0:35:34 > 0:35:36That's why Julio's job is so important.
0:35:36 > 0:35:39Things like this clogging up the pump.
0:35:40 > 0:35:43- A trophy!- OK. - I'll put this on my wall!
0:35:48 > 0:35:49Que sus impresiones?
0:35:54 > 0:35:55Oh, my God, the stink!
0:35:56 > 0:36:01'Unblocking a mega-city's sewer by hand isn't just disgusting,
0:36:01 > 0:36:03'it's also impractical.'
0:36:05 > 0:36:09There's about 110 miles of sewer system here in Mexico City
0:36:09 > 0:36:10and only two guys...
0:36:14 > 0:36:16..to keep the whole thing unblocked.
0:36:16 > 0:36:19It really is just a sticking plaster solution.
0:36:20 > 0:36:22This is tequila?
0:36:25 > 0:36:26Salute.
0:36:26 > 0:36:28Salud.
0:36:28 > 0:36:30Buena leche!
0:36:30 > 0:36:32- Ah, that's good.- Hmm?
0:36:32 > 0:36:34- That is good!- Thank you very much! - You're my hero.
0:36:43 > 0:36:47Mexico City's problem is growing worse as it continues to expand.
0:36:47 > 0:36:51Julio and his dive team are the old-world solution.
0:36:55 > 0:36:59Mexico City is entering a new age.
0:37:07 > 0:37:10Whether you're fixing up your house
0:37:10 > 0:37:12or you are in charge of an entire mega-city,
0:37:12 > 0:37:14as every builder will tell you,
0:37:14 > 0:37:18eventually, you have to get your drains sorted out properly.
0:37:19 > 0:37:23And this is something Mexico City is coming to terms with.
0:37:32 > 0:37:35This is the world's biggest sewer and wastewater pipe.
0:37:35 > 0:37:39It's seven metres in diameter, and when it's finished, it's going
0:37:39 > 0:37:43to be 39 miles long and capable of being able to get rid of
0:37:43 > 0:37:46150 cubic metres of water per second.
0:37:46 > 0:37:50That's the equivalent of 150,000 people flushing their loo,
0:37:50 > 0:37:52all at the same time.
0:38:01 > 0:38:06Six tunnel-boring machines are digging, day and night.
0:38:09 > 0:38:13It's a carefully choreographed process that leaves behind
0:38:13 > 0:38:1675 metres of brand new pipe every day.
0:38:24 > 0:38:27This machine is much more than just a digger.
0:38:27 > 0:38:29It's a tunnel-making factory.
0:38:51 > 0:38:53As it moves through the earth,
0:38:53 > 0:38:56concrete sections are bolted into place, sealing the walls.
0:39:02 > 0:39:05Leaving behind a finished, watertight tunnel.
0:39:14 > 0:39:15The ironic thing about this tunnel
0:39:15 > 0:39:19is that it's actually rather beautiful, you know.
0:39:19 > 0:39:22It's dramatic, it's aesthetically satisfying,
0:39:22 > 0:39:24it's meticulously constructed.
0:39:25 > 0:39:29But no-one's ever, ever going to see it, apart from you guys, obviously.
0:39:29 > 0:39:31You know, they're going to have an opening ceremony,
0:39:31 > 0:39:33and they're going to cut the red ribbon,
0:39:33 > 0:39:36and the only thing that's going to come through here is you-know-what!
0:39:59 > 0:40:03Right across the globe, over 300 huge machines are tunnelling
0:40:03 > 0:40:06beneath our feet, transforming the world we live in.
0:40:08 > 0:40:11Under the Swiss Alps, the world's longest tunnel
0:40:11 > 0:40:14will create a new artery to keep Europe on the move.
0:40:16 > 0:40:19In London, the vast Crossrail project is tunnelling
0:40:19 > 0:40:22from east to west, to move millions of people across the capital.
0:40:25 > 0:40:28And beneath New York, the largest construction project
0:40:28 > 0:40:31in the city's history is modernizing its water supply.
0:40:33 > 0:40:36From the inside out, we're redesigning our planet
0:40:36 > 0:40:39to cope with its ever-expanding population.
0:40:51 > 0:40:56This is Cleo, and she came into the world on June 6th at 10:08.
0:40:56 > 0:40:58This is Ellis Louis Marie,
0:40:58 > 0:41:03and he was born early hours of Monday the 4th of June.
0:41:04 > 0:41:07This is Jaden Grusset, and he was born on the 3rd of June.
0:41:07 > 0:41:12He doesn't have a name yet, but he was born at 3:30 this morning.
0:41:15 > 0:41:17Can't even begin to fathom what she's going to be.
0:41:17 > 0:41:19Maybe an astronaut.
0:41:19 > 0:41:23I hope he takes after me, like, into drama and music and dancing.
0:41:23 > 0:41:25Save the world, maybe.
0:41:25 > 0:41:28Go and be a Greenpeace conservationist,
0:41:28 > 0:41:29that would be quite cool.
0:41:29 > 0:41:32Oh, my God! Well, if his dad and his brother are anything to go by,
0:41:32 > 0:41:34probably a racing-car driver.
0:41:34 > 0:41:35Or his brother wants to be a ninja.
0:41:44 > 0:41:47All babies are special, but one new arrival
0:41:47 > 0:41:49could be very, very special indeed.
0:41:52 > 0:41:55This little fellow was actually born yesterday,
0:41:55 > 0:41:58which was also the day that the United Nations declared
0:41:58 > 0:42:02that the human population has hit seven billion.
0:42:02 > 0:42:05So I suppose this little guy has got as much claim
0:42:05 > 0:42:09as any other baby anywhere else in the world who was born yesterday
0:42:09 > 0:42:10to be number seven billion.
0:42:10 > 0:42:13But what I find amazing is that since my birth,
0:42:13 > 0:42:16the population has doubled.
0:42:16 > 0:42:21We've never seen such a dramatic population explosion in our history.
0:42:28 > 0:42:31Let me try and put a population of seven billion into perspective.
0:42:31 > 0:42:35If you wanted to count to seven billion out loud
0:42:35 > 0:42:38it would take you more than 200 years.
0:42:41 > 0:42:46It's been an estimated that one in 20 of all the people ever born
0:42:46 > 0:42:48are alive right now.
0:42:52 > 0:42:55Engineering a world that's fit for so many of us
0:42:55 > 0:42:57has called for some pretty quick changes.
0:43:00 > 0:43:02One country's speed of transformation
0:43:02 > 0:43:05leaves everywhere else standing.
0:43:05 > 0:43:08Hello, ni hao! How are you? Thank you, thank you.
0:43:15 > 0:43:17If you were going to count which of the world's skylines
0:43:17 > 0:43:21had the most cranes, or where the bulk of the world's concrete
0:43:21 > 0:43:24was being poured, or follow one of the biggest, fastest
0:43:24 > 0:43:28human migrations in history, all roads lead to China.
0:43:30 > 0:43:35Welcome to Shanghai, one of China's largest cities.
0:43:35 > 0:43:39Its skyline is vast, dramatic, futuristic,
0:43:39 > 0:43:43and it's been built almost from scratch over the last 20 years.
0:43:47 > 0:43:50China's mass migration from the countryside to the city
0:43:50 > 0:43:52began 30 years ago.
0:43:52 > 0:43:57Now, every week, 10,000 people make Shanghai their new home.
0:43:59 > 0:44:02To accommodate all those new arrivals,
0:44:02 > 0:44:04the city has been building at breakneck pace.
0:44:07 > 0:44:11One man has a very special record of the changes to his home town.
0:44:13 > 0:44:16'When Yao Jianliang started taking photographs,
0:44:16 > 0:44:20'he had no idea he was producing a unique document.'
0:44:20 > 0:44:24Wow, what a view. How often do you come up here to take photographs?
0:44:26 > 0:44:28Can I have a look? At your photos.
0:44:28 > 0:44:29- Can I see them?- OK.
0:44:32 > 0:44:36So this is this exact area, this is right here. OK.
0:44:36 > 0:44:39There we go. 1990, nothing there at all.
0:44:39 > 0:44:41That's just completely flat. From 1990 to now,
0:44:41 > 0:44:45I mean, you can see, it's just extraordinary, isn't it?
0:45:00 > 0:45:04You know, the terrifying thing that I've just realized is that
0:45:04 > 0:45:07I've got DIY projects in my house that have taken longer
0:45:07 > 0:45:10than it's taken Shanghai to build an entire city.
0:45:13 > 0:45:17These photos are a unique record of just how fast human beings
0:45:17 > 0:45:21can change the world if they put their minds to it.
0:45:21 > 0:45:24Their minds, and a couple of 100,000 builders, obviously.
0:45:30 > 0:45:34This accelerated change is now happening all over China.
0:45:35 > 0:45:39In the next ten years, around 350 million people
0:45:39 > 0:45:41are expected to head into its cities.
0:45:41 > 0:45:45That's almost six times the population of the UK
0:45:45 > 0:45:46looking for a new home.
0:45:48 > 0:45:52To accommodate everyone they'll need to build at lightning speed.
0:45:57 > 0:46:01One company in Southern China says it can build a 30-storey building
0:46:01 > 0:46:05from start to finish in less than three weeks.
0:46:05 > 0:46:08This is like doing flat-packed furniture at home,
0:46:08 > 0:46:11but this is just much larger scale.
0:46:13 > 0:46:16This building will be finished in 15 days. That's all we need.
0:46:29 > 0:46:32Their secret is to prefabricate as much as possible
0:46:32 > 0:46:34in their factory beforehand.
0:46:37 > 0:46:39So this is the floor unit.
0:46:39 > 0:46:45It contains the wiring, the air conditioning, the water supply,
0:46:45 > 0:46:47and the fire protection.
0:46:47 > 0:46:49So everything is fitted here to save time.
0:46:55 > 0:46:59Once delivered to the site, it's a race against time
0:46:59 > 0:47:01to link all the flat-pack sections together.
0:47:02 > 0:47:05200 engineers work day and night in rolling shifts.
0:47:08 > 0:47:11Another night, another floor!
0:47:13 > 0:47:17After seven days, the Chinese team have completed 18 storeys,
0:47:17 > 0:47:20about 60 metres of finished building.
0:47:25 > 0:47:28As well as being built at incredible speed,
0:47:28 > 0:47:31it's also designed to withstand a magnitude nine earthquake.
0:47:37 > 0:47:39It is an extraordinary achievement.
0:47:39 > 0:47:43In just over a couple of weeks, they've erected a building
0:47:43 > 0:47:46capable of housing more than 1,000 people.
0:47:49 > 0:47:52China is relying on innovative engineering like this.
0:47:54 > 0:47:57It has to, when migration into its cities is so rapid.
0:47:57 > 0:48:01Around 100 new tower blocks are needed every week,
0:48:01 > 0:48:03just to keep up.
0:48:06 > 0:48:09Across the planet a vast migration is taking place.
0:48:10 > 0:48:14Hundreds of thousands of us arrive in the world's cities every day,
0:48:14 > 0:48:17and they're groaning under the strain.
0:48:17 > 0:48:20Half of the population of Caracas now live in slums.
0:48:22 > 0:48:25In Mumbai, over six million of the city's population
0:48:25 > 0:48:28are crammed into barely 6% of its living space.
0:48:30 > 0:48:32And in Lagos, 70% of the residents
0:48:32 > 0:48:36make up one of the largest slums on the planet.
0:48:36 > 0:48:41In our new urban world, there are now over one billion squatters.
0:48:47 > 0:48:50This is Earth's biggest construction project.
0:48:50 > 0:48:54Well, at least part of it. And this is Uberajara, the man behind it.
0:48:57 > 0:49:00Now, it may not look much at the moment,
0:49:00 > 0:49:02but people like him are laying more bricks,
0:49:02 > 0:49:05they're pouring more concrete,
0:49:05 > 0:49:07building more houses than any place on Earth,
0:49:07 > 0:49:09and if you look around here,
0:49:09 > 0:49:12these are actually the cities of the future.
0:49:15 > 0:49:18Here in Brazil, slums are known as favelas.
0:49:18 > 0:49:24Rio alone has over 700 of them, home to up to 1.5 million people.
0:49:24 > 0:49:28That's about double the population of Leeds, crammed into slums.
0:49:32 > 0:49:34This is Daniella.
0:49:34 > 0:49:38She's eight months pregnant and the reason for this project.
0:49:38 > 0:49:41Her family have been slowly extending this house
0:49:41 > 0:49:43for four generations.
0:49:44 > 0:49:48It was Daniella's great-grandfather who laid the first bricks
0:49:48 > 0:49:51in this house, and as time went by and the family expanded,
0:49:51 > 0:49:54future generations built more and more rooms.
0:49:55 > 0:49:59Thousands of families extend their homes in this way,
0:49:59 > 0:50:03and it's this chaotic approach to urban planning
0:50:03 > 0:50:06that makes districts like this so cramped and overcrowded.
0:50:17 > 0:50:21Slums or shanty towns, favelas, whatever you want to call them,
0:50:21 > 0:50:24wherever you are in the world, they get a lot of bad press.
0:50:24 > 0:50:27But the city of Rio, cleverly, has realised, actually,
0:50:27 > 0:50:30you're never going to eradicate them.
0:50:30 > 0:50:33The best way to deal with them is to embrace them.
0:50:33 > 0:50:36And a central part of their plan is passing above my head right now.
0:50:43 > 0:50:48Rio has built the most extensive urban cable car system in the world.
0:50:52 > 0:50:56And it's had a profound effect on the residents of the favelas.
0:50:58 > 0:51:01Where they used to be isolated from the rest of the city,
0:51:01 > 0:51:06now the cable car lets them fly above the chaotic streets below.
0:51:13 > 0:51:15It is a genius solution, isn't it?
0:51:15 > 0:51:18Suddenly, all the people who live deep in the favela there
0:51:18 > 0:51:21have quick and easy access to the rest of the city,
0:51:21 > 0:51:23something that they just didn't have before.
0:51:26 > 0:51:29It's an investment the city hopes will transform people's lives.
0:51:33 > 0:51:35OK, I'm going to try a little experiment just to show you
0:51:35 > 0:51:37how much things have changed.
0:51:37 > 0:51:39This is Hamaris and Romerio.
0:51:39 > 0:51:42I'm going to go to that yellow cable car station over there
0:51:42 > 0:51:44using the actual cable car itself.
0:51:44 > 0:51:47And these two guys are going to run at ground level
0:51:47 > 0:51:49over there as fast as they can.
0:51:49 > 0:51:52Are you ready? Three, two, one, run!
0:52:08 > 0:52:09Here we go.
0:52:15 > 0:52:18Of course, I've got the easy option. The boys' journey
0:52:18 > 0:52:22is a baffling labyrinth of narrow streets and endless steps.
0:52:23 > 0:52:27You can see just how densely populated all the houses are.
0:52:27 > 0:52:30There's absolutely no way you could drive in between the houses,
0:52:30 > 0:52:35let alone set up a bus system or a tram system or anything like that.
0:52:35 > 0:52:39And travelling on foot means being careful to avoid crime hotspots.
0:52:42 > 0:52:44The great thing about this gondola system
0:52:44 > 0:52:46is that the stations themselves, they've got a police station,
0:52:46 > 0:52:49they've got a health centre, a community centre.
0:52:49 > 0:52:53They have become these integral parts of the entire community.
0:52:55 > 0:52:58The houses are so tightly packed together,
0:52:58 > 0:53:02engineers had to lay the cables painstakingly across the rooftops,
0:53:02 > 0:53:05before raising them to a height of over 30 metres.
0:53:09 > 0:53:12OK, so that is about, what?
0:53:12 > 0:53:15Three-and-a-half minutes from that station to this station,
0:53:15 > 0:53:18something like that. Wonder how my pals are getting on.
0:53:21 > 0:53:25The cable car has only been open since July 2011
0:53:25 > 0:53:28and it's already transforming this area.
0:53:30 > 0:53:32Thriving property market.
0:53:32 > 0:53:36Our local friendly estate agent tells us, nine months ago, 10 grand.
0:53:36 > 0:53:38Post cable-car, 30 grand.
0:53:39 > 0:53:40But they'll take an offer.
0:53:42 > 0:53:46Darkness falls and there's still no sign of the boys.
0:53:46 > 0:53:51In fairness, sunset's pretty rapid in this part of the world.
0:53:51 > 0:53:53Still, they have been gone for more than an hour.
0:53:56 > 0:53:58You made it!
0:53:59 > 0:54:03Very good! Very good! Well done! Well done!
0:54:06 > 0:54:10The cable car represents a brighter future for this area.
0:54:10 > 0:54:11And who knows?
0:54:11 > 0:54:15One day, this favela may become a sought-after place to live.
0:54:19 > 0:54:22But if you think that's an impossible dream,
0:54:22 > 0:54:26then look what happened somewhere a little closer to home.
0:54:26 > 0:54:30This is one of London's trendiest spots,
0:54:30 > 0:54:33and it's kind of a good example, actually, of how cities
0:54:33 > 0:54:34can radically change over time.
0:54:34 > 0:54:37This was one of the worst slums in all of London,
0:54:37 > 0:54:39one of the worst slums in all of Europe.
0:54:39 > 0:54:41Now look at it.
0:54:43 > 0:54:49This is Notting Hill in London, famous for a film, a carnival
0:54:49 > 0:54:52and astronomical house prices.
0:54:53 > 0:54:56It's quite a lot, £1,600 a week.
0:54:56 > 0:55:00If I wanted to buy it, what would that house be worth now?
0:55:00 > 0:55:03Probably looking at about 2.5 million.
0:55:03 > 0:55:05See, that's ridiculous.
0:55:05 > 0:55:07You've got Holland Park Tube two minutes away,
0:55:07 > 0:55:09the park itself is five minutes away.
0:55:09 > 0:55:13There's a roof terrace on the top, there's open-plan living,
0:55:13 > 0:55:14there's modern bathrooms.
0:55:14 > 0:55:17It's a good kind of fashionable area, community feel,
0:55:17 > 0:55:18it's really nice.
0:55:18 > 0:55:20- Two million, can I get it for that? - Nope.
0:55:20 > 0:55:24- Seriously?- Yep, most things go for asking price around here.
0:55:26 > 0:55:30But that's not how Charles Dickens saw it.
0:55:31 > 0:55:33I've got my own particulars here,
0:55:33 > 0:55:38- this is the same description of the same street but from 1850.- OK.
0:55:38 > 0:55:40OK, so this was when Charles Dickens was writing
0:55:40 > 0:55:42and sort of chronicling the area.
0:55:42 > 0:55:44"There are foul ditches, open sewers,
0:55:44 > 0:55:46"defective drains, smelling most offensively
0:55:46 > 0:55:49"and generating large quantities of poisonous gases."
0:55:49 > 0:55:52"Stagnant water is found at every turn,
0:55:52 > 0:55:55"not a drop of clean water can be obtained.
0:55:55 > 0:55:59"All is charged to saturation with putrescent matter."
0:55:59 > 0:56:01- Grotty.- Sounds disgusting!
0:56:01 > 0:56:04And you're trying to charge me 2.5 million for the house!
0:56:04 > 0:56:06You can't... I mean look at it, it's in black...
0:56:06 > 0:56:09There's Charles Dickens! Anyway. I'll take it!
0:56:13 > 0:56:16Not every slum is going to turn into Notting Hill,
0:56:16 > 0:56:20but the moral of the story is cities do change,
0:56:20 > 0:56:22because they have to.
0:56:27 > 0:56:29Our population has exploded,
0:56:29 > 0:56:32and the modern urban world is taking up the strain.
0:56:34 > 0:56:38This is Tokyo, the biggest city the world has ever seen.
0:56:42 > 0:56:45In little more than a generation, it's trebled in size.
0:56:45 > 0:56:49It's an intricate man-made landscape,
0:56:49 > 0:56:51covering an area eight times the size of London.
0:56:54 > 0:56:57A generation ago, a city of this scale
0:56:57 > 0:56:59would have been inconceivable.
0:57:02 > 0:57:07But in the future, there will be more cities of over 30 million.
0:57:08 > 0:57:12And we've already seen a glimpse of what they may look like.
0:57:17 > 0:57:21'Super-tall buildings will make the most of the space above ground...
0:57:25 > 0:57:28'..and giant tunnelling machines will open up the earth below.'
0:57:30 > 0:57:32Hello!
0:57:32 > 0:57:34'With human ingenuity,
0:57:34 > 0:57:39'our ability to redesign the planet is almost limitless.'
0:57:47 > 0:57:52I think that this is up there with any natural landscape.
0:57:53 > 0:57:56But cities aren't just about buildings and boxes
0:57:56 > 0:57:58and roads and railways.
0:57:58 > 0:58:00They're about something much more important.
0:58:00 > 0:58:02Ultimately, they are about us.
0:58:09 > 0:58:14As a species, we seem to thrive living together in our millions.
0:58:15 > 0:58:20We've become an urban animal and we've chosen a future
0:58:20 > 0:58:23that will have a man-made world at its heart.
0:58:49 > 0:58:52Subtitles by Red Bee Media Ltd