0:00:12 > 0:00:15As a geologist, I'm fascinated by rocks.
0:00:15 > 0:00:19But it's not just where they've come from, or what they're made of.
0:00:19 > 0:00:23It's the fundamental role they've played in shaping human history.
0:00:23 > 0:00:29In this series, I'm travelling around the Pacific Rim, on a quest
0:00:29 > 0:00:33through some of the most dramatic and exotic locations on Earth,
0:00:33 > 0:00:37to discover how civilisation's been moulded by the rocks beneath us.
0:00:43 > 0:00:47It's brought me to the rugged, vertical landscape of the Peruvian Andes,
0:00:47 > 0:00:51home to the highest peaks of the Western Hemisphere,
0:00:51 > 0:00:56and some of the world's most unpredictable and destructive climates.
0:01:00 > 0:01:05It's a land shaken by earthquakes and devastated by volcanoes.
0:01:05 > 0:01:11Yet 500 years ago, this inhospitable terrain was mastered by the Incas.
0:01:11 > 0:01:17The Inca civilization built a magnificent empire
0:01:17 > 0:01:22equivalent to Ancient Rome's, in one of the most hostile places on the planet.
0:01:22 > 0:01:27I'm going to journey through modern Peru, from coastal desert
0:01:27 > 0:01:29to oxygen-starved peaks.
0:01:29 > 0:01:33I want to uncover the geological challenges that they faced,
0:01:33 > 0:01:36and discover the secret of the Incas' triumph.
0:01:43 > 0:01:47On the eastern edge of the Pacific Rim, the South American continent
0:01:47 > 0:01:52is shaped by the 7,000-km long Andes mountain range.
0:01:54 > 0:01:57These mountains were the spine of the Inca Empire.
0:01:58 > 0:02:01To grasp the implications of this,
0:02:01 > 0:02:04I've come to look at a hole in the ground.
0:02:08 > 0:02:14If that stone keeps falling down to the deepest part of this great gash in the landscape,
0:02:14 > 0:02:17it will have dropped more than 4,100 metres.
0:02:17 > 0:02:20That's almost 13,500 feet.
0:02:20 > 0:02:22This is the Colca Canyon.
0:02:25 > 0:02:28The deepest canyons in the world
0:02:28 > 0:02:32lie crumpled in the heart of the Peruvian Andes.
0:02:35 > 0:02:40It's so difficult to get a sense of scale in this vast space,
0:02:40 > 0:02:42but to give you an idea, over there,
0:02:42 > 0:02:45that white patch clinging to the other side of the canyon
0:02:45 > 0:02:48is a village.
0:02:53 > 0:02:57The Colca Canyon is twice as deep as the Grand Canyon in America.
0:02:57 > 0:03:00It's home to these magnificent condors,
0:03:00 > 0:03:04the largest birds of prey in the world.
0:03:17 > 0:03:22Coping with the heights and chasms of the Andes was just one part
0:03:22 > 0:03:26of the geological challenge that confronted the Incas.
0:03:29 > 0:03:34Along the line of the Andes, there's a chain of dozens of active volcanoes,
0:03:34 > 0:03:36all capable of erupting.
0:03:36 > 0:03:39There's one volcano up there, Mount Hualca Hualca.
0:03:39 > 0:03:43And over here down in the canyon, you can see the vertical columns
0:03:43 > 0:03:47of a massive lava flow. What's more,
0:03:47 > 0:03:51the ground beneath me is frequently shattered by terrible earthquakes.
0:03:51 > 0:03:58I find it extraordinary that the Incas not only survived in this volatile geological setting,
0:03:58 > 0:04:01they thrived in it.
0:04:04 > 0:04:08More than ten million people lived under Inca rule,
0:04:08 > 0:04:12in villages and towns nestled amongst the Andean peaks.
0:04:17 > 0:04:23I want to know how they constructed buildings that survived the violent seismic activity of this region.
0:04:26 > 0:04:31How did they grow crops to feed their millions on such steep slopes,
0:04:31 > 0:04:36in such a hostile climate, and at such high altitude?
0:04:37 > 0:04:42How did they manage to link up the far-flung corners of their vast empire,
0:04:42 > 0:04:48an empire that sprawled over nearly a million square kilometres of geological extremes?
0:04:52 > 0:04:58By 1530, the Inca Empire covered not just most of what's now modern Peru,
0:04:58 > 0:05:01but much of what became Bolivia, Chile,
0:05:01 > 0:05:04and even parts of Argentina and Ecuador.
0:05:04 > 0:05:07A realm ruled by emperors
0:05:07 > 0:05:11who claimed divine consent from the Inca Sun God.
0:05:14 > 0:05:17Within its borders lay an extraordinary mix
0:05:17 > 0:05:20of ecological and geological zones,
0:05:20 > 0:05:25from snow-capped mountains to arid deserts.
0:05:26 > 0:05:29The remains of the great Inca Empire
0:05:29 > 0:05:35can be found even here, rising from the sands of Peru's Pacific coast.
0:05:36 > 0:05:40What marked the Incas out from all the Andean civilisations
0:05:40 > 0:05:43that had preceded them was how they mastered highland and lowland.
0:05:43 > 0:05:47I'm hoping that by looking at some of these ecological zones,
0:05:47 > 0:05:50I'm gonna get a better understanding of how they did it.
0:05:50 > 0:05:56And I'm gonna start down there, with a journey along Peru's great coast, on the Pan-American Highway.
0:06:06 > 0:06:10My first task is to find out how the Incas were able
0:06:10 > 0:06:14to keep their empire fed, when challenged with such unforgiving terrain.
0:06:19 > 0:06:24Lucio is our driver on this journey, and the landscape he reveals
0:06:24 > 0:06:27as we drive alongside the Pacific is unique.
0:06:27 > 0:06:30Almost all coastal Peru is the same,
0:06:30 > 0:06:36bleak desert, little rain, and, just as it was 500 years ago, mostly impossible to farm.
0:06:36 > 0:06:40But for the Incas, this barren coast was still a vital resource.
0:06:40 > 0:06:43And it was all down to geology.
0:06:43 > 0:06:49Parallel to this road there lies a deep oceanic trench that channels
0:06:49 > 0:06:53unusually cold water along these shores.
0:06:53 > 0:06:58This cold water sustains conditions perfect for an abundance of fish.
0:06:58 > 0:07:01In fact, these are the richest fisheries in the world.
0:07:05 > 0:07:07500 years ago,
0:07:07 > 0:07:11the vessels that fished Peru's waters couldn't be made out of wood.
0:07:11 > 0:07:16Trees are rare on this desert coast - it's just too dry.
0:07:17 > 0:07:21But the Incas had a way around this shortage - their fishermen
0:07:21 > 0:07:24made boats out of reed.
0:07:24 > 0:07:29The original design, unchanged since Inca times,
0:07:29 > 0:07:32is still used in a few places today.
0:07:32 > 0:07:36These are the Caballitos de Tortora - Horses of Reed.
0:07:36 > 0:07:38Hola, mi nombre Iain.
0:07:38 > 0:07:43- Mi nombre Luis.- Hiya. This is it. Caballitos.- Grande!
0:07:43 > 0:07:46Very "grande", isn't it? Gosh, amazing.
0:07:46 > 0:07:52..Could we? ..Looking forward to it.
0:07:57 > 0:08:01You must be very strong.
0:08:03 > 0:08:05Is it cold?
0:08:12 > 0:08:18The trick of it, as Luis attempts to explain,
0:08:18 > 0:08:23is to always point the nose of the Caballitos towards the oncoming waves.
0:08:27 > 0:08:32Get caught side on and you find out how cold the waters offshore really are.
0:08:38 > 0:08:41Luis and the fishermen here need only a couple of trips a day
0:08:41 > 0:08:45into these bountiful waters to sustain their communities.
0:08:45 > 0:08:52In theory, there's enough fish off this coast to feed an empire as large as the Incas.
0:08:52 > 0:08:57Perhaps they didn't need to bother with those inhospitable mountains after all.
0:08:58 > 0:09:01The coastal people here had the knowledge
0:09:01 > 0:09:05and the skills to fish these waters and make the most
0:09:05 > 0:09:08of what these arid shores have to offer.
0:09:08 > 0:09:10But there was one problem - El Nino.
0:09:12 > 0:09:16For centuries now, Peruvian fishermen have noticed
0:09:16 > 0:09:20that every few years, the waters offshore get warmer.
0:09:20 > 0:09:22Usually it happens around Christmas,
0:09:22 > 0:09:28so they started calling this warming El Nino - The Infant, after the Christ child.
0:09:29 > 0:09:33We now know that the knock-on effects of El Nino are global,
0:09:33 > 0:09:39from flooding in California to drought in Indonesia,
0:09:39 > 0:09:43but Peru's Pacific coast is where the phenomenon originates.
0:09:43 > 0:09:47It starts with a weakening of the normal coastal trade winds.
0:09:47 > 0:09:51We're not really sure why it happens, but we know the result.
0:09:51 > 0:09:56The waters out there get warmer by about 10C,
0:09:56 > 0:09:59distorting weather around the world.
0:09:59 > 0:10:02The impact in Peru is devastating.
0:10:10 > 0:10:14The warm El Nino waters change the balance of life
0:10:14 > 0:10:17in the seas - plankton die out, and fish levels plummet.
0:10:17 > 0:10:22The Incas would have faced this problem too,
0:10:22 > 0:10:26making reliance on fishing alone far too risky.
0:10:28 > 0:10:31For a sense of the El Nino effect in Inca times,
0:10:31 > 0:10:36I've come to the modern Peruvian fishing port of Chimbote.
0:10:36 > 0:10:41In 1972, 20% of global fishing took place in these waters,
0:10:41 > 0:10:45then came the worst El Nino in recorded history.
0:10:51 > 0:10:55It wiped out nearly 90% of Peruvian fish stocks,
0:10:55 > 0:10:58and just as it was getting back on its feet,
0:10:58 > 0:11:02the fishing industry here was hit by another severe El Nino.
0:11:02 > 0:11:09Many of the boats in Chimbote now spend several months of the year becalmed and inactive.
0:11:12 > 0:11:18There's no way to predict when this El Nino effect is gonna happen - it can arrive
0:11:18 > 0:11:20at intervals at anything between two and 11 years,
0:11:20 > 0:11:23and it can last up to 18 months.
0:11:25 > 0:11:28So for the Incas, depending on coastal fishing alone
0:11:28 > 0:11:31would have been a flawed strategy.
0:11:31 > 0:11:34To feed their empire, they had to find ways of exploiting
0:11:34 > 0:11:37their natural home in the inhospitable mountains.
0:11:37 > 0:11:40And that would be no easy task.
0:11:40 > 0:11:43I'm heading eastwards, and up, into the Andes,
0:11:43 > 0:11:48to Peru's fabled White City, to discover how the Incas did it.
0:11:58 > 0:12:02As we drive inland and uphill,
0:12:02 > 0:12:07I'm becoming aware of just how difficult this place must have been for the Incas to farm.
0:12:11 > 0:12:16There are steep slopes, poor soils, and the weather here
0:12:16 > 0:12:20is just as unhelpful as it is down on the coast.
0:12:25 > 0:12:29In Peru, each altitude zone has been given its own name.
0:12:29 > 0:12:33As we ascend between 500 metres and 2,300 metres,
0:12:33 > 0:12:35we drive through the Yunga zone.
0:12:35 > 0:12:39But we're heading higher still, into the Quechua zone.
0:12:43 > 0:12:49This is our destination, Arequipa - the White City.
0:12:50 > 0:12:54Buildings here are made from a white volcanic rock called sillar.
0:12:58 > 0:13:01Above this thriving modern city,
0:13:01 > 0:13:05the perfect cone of the volcano Mount Misti.
0:13:14 > 0:13:17As legend has it, Ancient Arequipa
0:13:17 > 0:13:22was named by an Inca emperor on his way back from a war of conquest.
0:13:22 > 0:13:26Exhausted, he arrived here and said, in the Inca language,
0:13:26 > 0:13:30"Arequipe", which means, "OK, let's stop here".
0:13:31 > 0:13:36Now that's a good idea. Arequipa is, at 2,300 metres,
0:13:36 > 0:13:43the start of the Quechua zone which extends upwards to about 3,500 metres.
0:13:43 > 0:13:47That's about three times the height of Mount Snowdon in Wales,
0:13:47 > 0:13:51which for those that live around here is a small hill.
0:13:51 > 0:13:55In Inca times, most people lived in this Quechua zone.
0:13:55 > 0:14:02Successfully cultivating the land at this altitude was a matter of life and death for the Incas.
0:14:03 > 0:14:09To find out how they did it, I'm meeting up with Juan Ossio, one of Peru's most eminent historians.
0:14:09 > 0:14:14Although I'm a little anxious about the Inca delicacy he's lined up for lunch...
0:14:14 > 0:14:17So tell me more about this.
0:14:17 > 0:14:22Well, you know, the name of this is quwi, and it has been known now
0:14:22 > 0:14:28in the wider world as a guinea pig, a delicacy for the Incas.
0:14:28 > 0:14:32This was an extremely tasteful course.
0:14:32 > 0:14:36I normally have my guinea pigs on a wheel - I've never had them round.
0:14:36 > 0:14:40So what were the challenges about growing food in this Quechua zone?
0:14:40 > 0:14:43Well, the main problem, I think,
0:14:43 > 0:14:48is the unpredictability of the weather.
0:14:48 > 0:14:53Either severe drought that may produce frost, or if you have an excessive amount of rain,
0:14:53 > 0:14:59the problem is that the crops that were grown by the Andean people may get rotten.
0:14:59 > 0:15:03- So either too little rain, drought, or too much rain. - That's the problem.
0:15:03 > 0:15:07It seems a very fragile environment. How did they manage to manage it?
0:15:07 > 0:15:13- The solution to sort out this problem was to develop land terraces. - Land terraces?- Land terraces.
0:15:23 > 0:15:25In the countryside around Arequipa,
0:15:25 > 0:15:30we can see how that Inca solution has transformed the landscape.
0:15:33 > 0:15:37Everywhere, there are terraces...and terraces...
0:15:37 > 0:15:40and terraces...
0:15:42 > 0:15:44..and terraces!
0:15:50 > 0:15:56It's said that the Incas approached farming with weapons in their hands and prayers on their lips.
0:15:56 > 0:16:02To them, agriculture was like warfare - a victory claimed
0:16:02 > 0:16:04by disembowelling the Earth.
0:16:13 > 0:16:16So, Juan, these terraces are absolutely stunning.
0:16:16 > 0:16:20- They are indeed beautiful.- But how do they work, what's their job?
0:16:20 > 0:16:22Well, they accomplish different purposes.
0:16:22 > 0:16:27One of the purposes was to face the unpredictability of the weather,
0:16:27 > 0:16:32another one was to expand the agricultural production, because, as you can see,
0:16:32 > 0:16:39the slopes are very steep so this is a good alternative for making those slopes productive.
0:16:39 > 0:16:42Apart from that, there is the problem of erosion as well.
0:16:42 > 0:16:47- So, what, they stabilise the slopes? - It stabilises extremely well.
0:16:47 > 0:16:52So in terms of the unpredictability of the weather, what? Do they capture the rainfall?
0:16:52 > 0:16:55Not the rainfall, but the water coming from the mountains.
0:16:55 > 0:16:59- So the mountain streams feed these? - The mountain streams, exactly.
0:16:59 > 0:17:05Irrigation like this, using water diverted from streams, is much more reliable than rainfall.
0:17:08 > 0:17:15As in Inca times, maize - that's corn - is the staple crop grown on these terraces.
0:17:15 > 0:17:20Juan has asked Don Geraldo, a local farmer, if we can attend
0:17:20 > 0:17:26an Inca ritual still performed when maize seeds are selected for planting.
0:17:30 > 0:17:32This is a private ritual -
0:17:32 > 0:17:36a practice that's widespread here, but rarely seen by outsiders.
0:17:44 > 0:17:48There is no crop so important as maize - the seed is so important
0:17:48 > 0:17:51that is treated very specially.
0:17:52 > 0:17:55- And this is Chicha? - And that is Chicha.
0:17:55 > 0:18:01Chicha, a beer brewed from maize, is at the sacred heart of the ceremony.
0:18:01 > 0:18:04He is offering to each of the mountains.
0:18:04 > 0:18:06And then to the maize.
0:18:09 > 0:18:13And now he spills some to the ground,
0:18:13 > 0:18:18- because that's the Mother Earth receiving too.- Pachamama. - That's it, Pachamama.
0:18:18 > 0:18:22- And then he drinks, obviously. - He has to drink the whole thing.
0:18:22 > 0:18:25- The whole thing? - The whole thing, yes.
0:18:29 > 0:18:30Wow.
0:18:32 > 0:18:35It's your turn.
0:18:35 > 0:18:37Thank you very much,
0:18:37 > 0:18:40- thank you. Muchas gracias. Is it strong?- No, it's very soft.
0:18:40 > 0:18:43This one is mild.
0:18:46 > 0:18:49It's quite strong, actually!
0:19:00 > 0:19:03Ah! Muchas gracias, muchas gracias.
0:19:04 > 0:19:10I read, I don't know if this is true, but in the Inca times the emperor had these virgins of the sun
0:19:10 > 0:19:13that chewed the maize and fermented the chicha.
0:19:13 > 0:19:17That is true, because saliva helps to ferment the chicha
0:19:17 > 0:19:20and it's something that has continued even to our times.
0:19:20 > 0:19:23Do you think this chicha was chewed by these ladies?
0:19:24 > 0:19:29I doubt, I imagine that this chicha has been prepared in a different way.
0:19:29 > 0:19:33Good, that makes me feel a little better!
0:19:36 > 0:19:40Well, now they continue with the selections of the seeds
0:19:40 > 0:19:44and that is a job performed exclusively by women.
0:19:44 > 0:19:47Men are never allowed to touch seeds.
0:19:47 > 0:19:50- To touch the seeds. - They are not allowed.
0:20:00 > 0:20:02Farming these slopes is a constant struggle.
0:20:02 > 0:20:09To thrive, maize needs a warm and humid climate and a relatively long growing season.
0:20:09 > 0:20:12Neither are assured at this altitude.
0:20:12 > 0:20:18Every year, the crops are menaced by drought, while frost remains a constant threat.
0:20:18 > 0:20:23As with the fishing on the coast, the Incas couldn't guarantee
0:20:23 > 0:20:28that the terraces would provide for their vast population in any given year.
0:20:28 > 0:20:33They needed to exploit every possible food source, wherever they found it.
0:20:33 > 0:20:38So Lucio and I are off again, heading uphill.
0:20:45 > 0:20:49As we drive higher, the mountains have become
0:20:49 > 0:20:51even more hostile.
0:20:51 > 0:20:57At this level, maize can't grow, and the soil is difficult to terrace.
0:20:58 > 0:21:03Yet Inca farmers still saw great potential in these highlands.
0:21:03 > 0:21:07We've now entered what's called the Suni zone,
0:21:07 > 0:21:11which lies between 3,500 and 4,000 metres.
0:21:11 > 0:21:16About three times as high as the UK's tallest mountain, Ben Nevis.
0:21:20 > 0:21:27The temperature here regularly dips below zero - shadows from passing clouds can reduce it
0:21:27 > 0:21:30by 15C in a moment.
0:21:30 > 0:21:33But the Incas had a very special crop that meant
0:21:33 > 0:21:37this Suni zone gave them some of their most productive land.
0:21:37 > 0:21:40To find it, I'm off shopping.
0:21:45 > 0:21:51What strikes me about the markets here is the amazing range of produce.
0:21:51 > 0:21:58In fact, it's thought that Andean inhabitants were the first to cultivate as many as half
0:21:58 > 0:22:02of the agricultural products the world grows today.
0:22:02 > 0:22:04Their inventiveness,
0:22:04 > 0:22:07a direct response
0:22:07 > 0:22:09to the challenging landscape around them.
0:22:11 > 0:22:16And in the Suni zone, one crop thrives...
0:22:16 > 0:22:17the humble spud.
0:22:17 > 0:22:21The potato was first cultivated in the Andes
0:22:21 > 0:22:24and there are hundreds of different varieties in these mountains.
0:22:24 > 0:22:28Because it grows underground, a tuber like the potato
0:22:28 > 0:22:33is protected from the bitter night-time cold at this altitude.
0:22:37 > 0:22:41Hola. Que es esta?
0:22:41 > 0:22:42Olloco.
0:22:42 > 0:22:49Olloco. OK, ah, tres. Tres.
0:22:49 > 0:22:52- They look nice. Esta?- Oca.- Oca.
0:22:52 > 0:22:55OK, oca. That looks fantastic.
0:22:55 > 0:22:58- Look at that. Que es?- Maca.
0:22:58 > 0:23:02Maca, maca, this is. I hear this is an aphrodisiac.
0:23:02 > 0:23:05Bueno, mucho bueno, eh? Dos, I better have.
0:23:07 > 0:23:10Try two...cinco soles.
0:23:10 > 0:23:12Muchas gracias. Adios.
0:23:13 > 0:23:19By capitalising on the sheer diversity of produce, from maize and other crops in the low valleys,
0:23:19 > 0:23:22to potatoes and related tubers up here,
0:23:22 > 0:23:28the Incas mastered survival at up to 4,000 metres. But they didn't just stop there.
0:23:28 > 0:23:31Some of the most important land was to be found higher still
0:23:31 > 0:23:34and to get there, we'll have to abandon the car,
0:23:34 > 0:23:37and use a more traditional means of getting around the Andes.
0:23:52 > 0:23:56I've persuaded Lucio, our driver, to continue as my guide.
0:23:56 > 0:24:00- These animals must walk slowly. - Right.
0:24:05 > 0:24:08There's a bit of a traffic jam here.
0:24:14 > 0:24:16Ah, you use this, do you?
0:24:18 > 0:24:22The Incas never used wheels for transport.
0:24:22 > 0:24:25As I hike up the rocks and ruts of this mountain trail,
0:24:25 > 0:24:27I'm beginning to understand why.
0:24:31 > 0:24:37We're gonna climb higher into the Puna zone, 4,000 metres
0:24:37 > 0:24:41and above. Few staple crops can grow in the Puna,
0:24:41 > 0:24:44but this zone was vital to the Incas.
0:24:44 > 0:24:48The reason, these pack animals - "yamas".
0:24:48 > 0:24:51Or as we say in English, "llamas".
0:24:51 > 0:24:56These animals were at the heart of the Inca economy.
0:24:56 > 0:24:59The Puna zone is where the llamas like to graze.
0:24:59 > 0:25:01They love the tough ichu grass
0:25:01 > 0:25:04which grows at this altitude.
0:25:04 > 0:25:07Llamas were a vital supply
0:25:07 > 0:25:08of leather and wool.
0:25:08 > 0:25:12They were even used as an offering to the Inca Sun God -
0:25:12 > 0:25:16every month, hundreds were sacrificed to appease him.
0:25:19 > 0:25:22They were crucial for carrying cargo.
0:25:22 > 0:25:27The Inca army used supply trains of thousands of llamas.
0:25:27 > 0:25:32And when they were no longer needed for porterage, they were eaten.
0:25:32 > 0:25:34I've an idea for a menu tonight,
0:25:34 > 0:25:38one of these llamas, he's got some tubers that I bought at the market.
0:25:38 > 0:25:42It's an, um, I don't know, one of the white ones, I think. OK.
0:25:42 > 0:25:48Fortunately for our woolly friends, tonight's meal will be strictly vegetarian.
0:25:51 > 0:25:56- So what's in the pot, then? - Well, we have some oca.
0:25:56 > 0:25:59- Oca, OK. - HE CHEWS
0:25:59 > 0:26:02Oh, that's nice. It's quite sweet.
0:26:02 > 0:26:08- Yeah, you put some sugar, it's better.- Sugar with potato?! - Yeah. Here we have some maca.
0:26:08 > 0:26:11Ah, I've heard, I've heard about this.
0:26:11 > 0:26:17- Yeah.- I'm not sure I should, you know there's like five men and eight llamas and I'm taking maca.
0:26:17 > 0:26:21- Is it, is it really an aphrodisiac? - People say that it is.
0:26:21 > 0:26:25Should I try this maca? No, he say no.
0:26:25 > 0:26:27Lucio, maca, they're all saying no.
0:26:27 > 0:26:29I don't think I should try this.
0:26:29 > 0:26:31'The tubers and the potatoes on the menu tonight
0:26:31 > 0:26:36'are high in carbohydrate - an excellent source of energy, and I'm going to need it.
0:26:36 > 0:26:40'Tomorrow, we're gonna attempt a difficult climb to the roof
0:26:40 > 0:26:44'of the Inca world, a place higher than I've ever been in my life.'
0:26:48 > 0:26:51It was really hot out there today, but it'll get very cold tonight -
0:26:51 > 0:26:55temperatures outside the tent are gonna drop to -5 Centigrade.
0:26:55 > 0:26:59So I'm all wrapped up, and I'll see you in the morning.
0:27:39 > 0:27:42We've climbed to about 4,300 metres,
0:27:42 > 0:27:46which is about 14,500 feet.
0:27:46 > 0:27:51If I seem a little breathless, it's because, at this high altitude,
0:27:51 > 0:27:55the air is beginning to get much thinner.
0:28:11 > 0:28:15Every breath I take feeds less oxygen to my brain
0:28:15 > 0:28:20and I'm in danger of suffering from altitude sickness, or hypoxia.
0:28:21 > 0:28:24The symptoms are headaches, shortage of breath,
0:28:24 > 0:28:26nausea and dizziness.
0:28:26 > 0:28:30I mean, I feel all right, but I've certainly lost my appetite
0:28:30 > 0:28:33and I don't think it's to do with last night's meal.
0:28:33 > 0:28:37But I do feel weak and the thing is, left to its worse,
0:28:37 > 0:28:40hypoxia could put me in a coma.
0:28:47 > 0:28:50But there was something remarkable about the Incas,
0:28:50 > 0:28:53and it's been passed on to their modern descendents.
0:28:53 > 0:28:58Compared to a lowlander like me, Andean people have hearts and lungs
0:28:58 > 0:29:01which are proportionately larger and take in more oxygen,
0:29:01 > 0:29:04adaptations shaped by their mountain home.
0:29:04 > 0:29:09For our guides, evolution has been influenced by geology.
0:29:10 > 0:29:13Lucio, how are you feeling?
0:29:13 > 0:29:15Good. I'm OK.
0:29:15 > 0:29:18- See, these guys they're just bounding up.- Yeah.
0:29:27 > 0:29:30There may be another secret to Inca resilience,
0:29:30 > 0:29:33and it's nothing to do with biological adaptation.
0:29:34 > 0:29:38Lucio, I think its time for those coca leaves.
0:29:38 > 0:29:43- Really?- Yeah, I got a terrible headache.- OK, I'm going to bring you some, I have some.
0:29:43 > 0:29:48'This is not cocoa as in chocolate, but coca, as in cocaine.'
0:29:48 > 0:29:52- Chew it.- Can you make cocaine from this? In Britain, this is illegal. - No, it's legal here.
0:29:52 > 0:29:56- For cocaine, you must to mix with chemicals.- So it's...
0:29:56 > 0:30:00This is natural, so it's legal here in Peru. You put it in your mouth
0:30:01 > 0:30:04and after, you start to roll it.
0:30:04 > 0:30:06- Roll it?- Exactly - roll it.
0:30:06 > 0:30:11- It's not gonna blow me away, go crazy?- No, it's like a coffee. - OK. Like a coffee?- Yeah.- OK.
0:30:11 > 0:30:14- I'll have a coffee.- You want more? - More?
0:30:14 > 0:30:16'Coca leaves are a stimulant.
0:30:16 > 0:30:21'A rolled wad of chewed leaves will provide my body with an energy boost
0:30:21 > 0:30:24'and the very act of chewing for several hours
0:30:24 > 0:30:29'can accelerate the digestion of high-carb foods, like last night's potatoes.'
0:30:43 > 0:30:46I've been chewing coca leaves for about three hours.
0:30:46 > 0:30:48My mouth is completely numb,
0:30:48 > 0:30:52but my headache's gone and I'm feeling kind of energetic -
0:30:52 > 0:30:56surprising, because this is the highest that I've been in my life.
0:31:03 > 0:31:08We've just passed the top of the Puna zone, at 4,800 metres.
0:31:15 > 0:31:18We're now higher than any peak in Europe.
0:31:22 > 0:31:26Because it's warmer here, near the equator, we're still below the snowline.
0:31:33 > 0:31:36Above this point is the Janca zone.
0:31:36 > 0:31:39Even the Incas had no need to venture up there.
0:31:39 > 0:31:40No crops would grow,
0:31:40 > 0:31:44and there was no possible grazing for the llamas.
0:31:48 > 0:31:50This is as high as I go.
0:31:50 > 0:31:55On my journey from this coast up into the mountains I've learned
0:31:55 > 0:31:59that these altitude zones are incredibly challenging to farming,
0:31:59 > 0:32:01the climate, totally unpredictable.
0:32:01 > 0:32:04The Inca solution was to spread the risk.
0:32:07 > 0:32:12They realised that if they exploited a number of different altitudes at the same time,
0:32:12 > 0:32:14it would not matter if one failed -
0:32:14 > 0:32:19the others might remain unaffected and keep the empire fed and stable.
0:32:19 > 0:32:22The trick was to think vertically.
0:32:23 > 0:32:27The Incas didn't just understand this, they actively studied it.
0:32:27 > 0:32:29We know this because of the existence
0:32:29 > 0:32:32of one the most remarkable archaeological sites in Peru.
0:32:32 > 0:32:36And thankfully, it's not up here, it's down there,
0:32:36 > 0:32:38where there's more oxygen.
0:32:49 > 0:32:51This is Moray.
0:32:56 > 0:32:59At first glance, these terraces,
0:32:59 > 0:33:02a succession of perfect concentric circles,
0:33:02 > 0:33:06seem like the remains of a religious site.
0:33:09 > 0:33:12But this was something far more surprising -
0:33:12 > 0:33:16500 years ago, this was a lab,
0:33:16 > 0:33:17a greenhouse.
0:33:17 > 0:33:22It's a relic of the Incas' agricultural prowess.
0:33:25 > 0:33:28Here, the Incas discovered that they could recreate
0:33:28 > 0:33:31the range of soils, temperatures and other variables
0:33:31 > 0:33:33found throughout the Andes.
0:33:33 > 0:33:35This was an experimental station
0:33:35 > 0:33:38where they could see which crops could survive where.
0:33:38 > 0:33:44And it was also a place where they could develop new strains to suit specific altitudes and conditions.
0:33:50 > 0:33:52In just this one small area,
0:33:52 > 0:33:56there could be as many as 20 ecological zones.
0:33:56 > 0:34:00All made possible by the particular geology of the site.
0:34:01 > 0:34:05The permeable limestone underneath soaks up the surface water,
0:34:05 > 0:34:08and because it's slightly acidic, it dissolves the rock
0:34:08 > 0:34:12leaving behind these holes, or craters in the landscape.
0:34:16 > 0:34:21The concentric nature of these bowls lets them capture sunlight and shade
0:34:21 > 0:34:25in a way that duplicates huge temperature variations.
0:34:25 > 0:34:29Just 30 metres separates the top and bottom terraces,
0:34:29 > 0:34:34yet a 16 degrees centigrade difference in temperature has been recorded.
0:34:34 > 0:34:41Down there, growing conditions replicate the Quechua zone at around 2,600 metres.
0:34:41 > 0:34:46Where I'm standing, it's more like the frosty Puna zone at 4,000 metres.
0:34:51 > 0:34:55The Incas probably measured the temperature differences
0:34:55 > 0:34:59by placing water in containers to freeze on the terraces overnight
0:34:59 > 0:35:03and monitoring the rate of thaw in the morning sunshine.
0:35:05 > 0:35:08What amazes me as a geologist
0:35:08 > 0:35:12is how the Incas turned this rugged topography to their advantage.
0:35:12 > 0:35:15The challenging Andean landscape was the problem,
0:35:15 > 0:35:18but it also provided its own solution.
0:35:18 > 0:35:21The essence of survival here was variety.
0:35:23 > 0:35:27By experimenting with crops and exploiting different altitudes,
0:35:27 > 0:35:31the Incas found ways to grow food for their millions.
0:35:31 > 0:35:35In fact, they could even produce a surplus.
0:35:35 > 0:35:38This was an amazing achievement,
0:35:38 > 0:35:41but it only solved part of their geological challenge.
0:35:41 > 0:35:46They needed to develop a storage and distribution network for their food.
0:35:46 > 0:35:49But how could they manage to do it in a place as rugged as this?
0:35:55 > 0:35:59I've come to the village of Ollantaytambo to find out.
0:35:59 > 0:36:05'It's a good place to look for clues because it's a bit like a walk back in time,
0:36:05 > 0:36:08'and taking it with me is Peter Frost, an English historian
0:36:08 > 0:36:11'who's made Peru his home for 18 years.'
0:36:13 > 0:36:16So what's so special about this Ollantaytambo?
0:36:16 > 0:36:22Well, its unique really because it's the only Inca settlement with an Inca town plan,
0:36:22 > 0:36:25the Inca streets, the Inca courtyards, in many cases,
0:36:25 > 0:36:27which are still inhabited.
0:36:33 > 0:36:37Each of these blocks would have been an Inca cancha, as they call them,
0:36:37 > 0:36:41like a courtyard with a number of buildings facing inwards,
0:36:41 > 0:36:45each of these inhabited by different members of the same kinship group.
0:36:51 > 0:36:54Ollantaytambo gives us a real insight
0:36:54 > 0:36:57into how the Incas organised their villages,
0:36:57 > 0:37:03and because the site is so well preserved, it reveals exactly how they stored their surplus food.
0:37:04 > 0:37:08The system that was developed by the Incas made it safer -
0:37:08 > 0:37:10they weren't so subject to famine and disaster,
0:37:10 > 0:37:14which is one of the ruling factors in the Andes.
0:37:14 > 0:37:17They stored their agricultural surplus
0:37:17 > 0:37:21in a vast network of storehouses that were scattered throughout the empire.
0:37:21 > 0:37:26- There's one right there on that mountain, you see?- Er, no.- It's just above the trees over there -
0:37:26 > 0:37:30there's three lines, three rows of storehouses there.
0:37:30 > 0:37:36- Precariously balanced on the rock face, that's where they put their warehouses?- Yes,
0:37:36 > 0:37:39they built them in high, inaccessible places for various reasons.
0:37:39 > 0:37:43Firstly it was a good place to keep produce fresh
0:37:43 > 0:37:46because it was windy and cool.
0:37:46 > 0:37:51It was also inaccessible, so unauthorised people couldn't get to it very easily.
0:37:51 > 0:37:53And another is perhaps to make it very prominent
0:37:53 > 0:37:59so people are always aware that these storehouses are there for their benefit.
0:37:59 > 0:38:04- Like a big neon sign saying, "Inca will look after you", or something?- In a sense, yes.
0:38:05 > 0:38:10'So Inca storehouses acted like shock absorbers
0:38:10 > 0:38:11'to stabilise their empire,
0:38:11 > 0:38:17'providing access to food in times of poor harvests, adverse weather and famine.
0:38:17 > 0:38:22'But without a means of distribution, these storehouses were of little use
0:38:22 > 0:38:25'and for that, the Incas needed roads.'
0:38:27 > 0:38:31It seems inconceivable in the difficult terrain of the Andes,
0:38:31 > 0:38:36but the Inca Empire was bound together by a 40,000km road network.
0:38:36 > 0:38:43And as the Incas hadn't developed the wheel, these roads were designed for travel by foot.
0:38:43 > 0:38:46They had sophisticated drainage
0:38:46 > 0:38:48and kilometres of steps were built for the slopes,
0:38:48 > 0:38:52all done with simple bronze tools.
0:38:52 > 0:38:55These roads could be used to transport food
0:38:55 > 0:38:58and were a key means of administering the empire.
0:38:58 > 0:39:02State officials travelled along them, and so did information.
0:39:02 > 0:39:06Special couriers called chaskis would transmit messages
0:39:06 > 0:39:10across the empire by running relays along roads like these.
0:39:10 > 0:39:13They operated from stations at regular intervals
0:39:13 > 0:39:18and could cover 240km, that's 150 miles, each day,
0:39:18 > 0:39:22which is hugely impressive given this rugged landscape.
0:39:24 > 0:39:28Chaski were trained from childhood to remember verbal messages perfectly.
0:39:28 > 0:39:31Flawless accuracy was almost guaranteed
0:39:31 > 0:39:36because they would suffer severe punishments if errors crept in.
0:39:36 > 0:39:40Verbal messages were not the only thing the chaskis relayed -
0:39:40 > 0:39:44they also carried these pieces of knotted string, called khipus.
0:39:44 > 0:39:47These were enormously important to the Incas
0:39:47 > 0:39:49because they didn't have a written language.
0:39:49 > 0:39:54They used the knots in these khipus to record statistical information
0:39:54 > 0:39:56vital to the running of the empire.
0:39:56 > 0:40:00For example, how much was contained in each of the storehouses
0:40:00 > 0:40:03in times of emergency.
0:40:04 > 0:40:07It seems the Incas had developed a system
0:40:07 > 0:40:12that mastered the difficulties of building an empire at high altitude.
0:40:12 > 0:40:14But unfortunately for them,
0:40:14 > 0:40:19extreme weather and topography were only part of their challenge -
0:40:19 > 0:40:25all their structures had to survive the frequent earthquakes that strike this volatile region.
0:40:26 > 0:40:33Recent natural disasters in Peru can give us a feel for what confronted the Incas 500 years ago.
0:40:35 > 0:40:39I'm back on the road with Lucio to show you what I mean.
0:40:39 > 0:40:44We're travelling northwest to the tragic market town of Yungay.
0:40:46 > 0:40:48FESTIVE MUSIC PLAYS
0:40:48 > 0:40:53En route, we encounter an colourful roadblock, a fiesta.
0:41:00 > 0:41:04In the Andes, they're a frequent and raucous celebration of life.
0:41:10 > 0:41:14On Sunday 31st May 1970,
0:41:14 > 0:41:18Yungay was celebrating an unusual fiesta of its own.
0:41:18 > 0:41:21It was the first day of the Mexico World Cup finals
0:41:21 > 0:41:23and Peru had qualified.
0:41:28 > 0:41:31Yungay sprawled in the shadow of Huascaran,
0:41:31 > 0:41:36at nearly 7,000 metres, the highest peak in all the Peruvian Andes.
0:41:43 > 0:41:46That afternoon, tragedy struck Yungay -
0:41:46 > 0:41:50a massive earthquake shook the central part of Peru.
0:41:50 > 0:41:53Measuring 7.8 on the Richter scale,
0:41:53 > 0:41:58it was the equivalent power of 400 Hiroshima atomic bombs.
0:41:58 > 0:42:01The quake caused death and devastation in many cities.
0:42:07 > 0:42:10In Yungay, however, the worst was yet to come.
0:42:10 > 0:42:15The earthquake had triggered an enormous landslide up there on Huascaran.
0:42:15 > 0:42:19The slide took just three minutes to travel the 18 kilometres
0:42:19 > 0:42:21from up there to Yungay,
0:42:21 > 0:42:27covering the town in a layer of rock, ice and mud 70 metres deep.
0:42:27 > 0:42:29According to official figures,
0:42:29 > 0:42:3313,000 people lie buried beneath my feet.
0:42:37 > 0:42:40This satellite image shows Yungay before the earthquake.
0:42:44 > 0:42:45And this, after -
0:42:45 > 0:42:50the town submerged under the landslide's white mass.
0:42:54 > 0:42:58This may look like a rock, but it's the top of a church spire,
0:42:58 > 0:43:02all that emerges from the now solid layer of mountain debris.
0:43:05 > 0:43:09This is what a bus looks like when crushed together by a landslide.
0:43:14 > 0:43:17On Huascaran, you can still see the scar
0:43:17 > 0:43:22where 50 million cubic metres of the mountain just sheared off.
0:43:32 > 0:43:34There were a few survivors.
0:43:35 > 0:43:39One small group had been visiting the local cemetery, on this hill.
0:43:42 > 0:43:48What happened here was the worst earthquake-triggered landslide in recorded history.
0:43:51 > 0:43:56Earthquakes occur because the planet is covered in a patchwork of plates
0:43:56 > 0:43:58floating on a plasticky interior.
0:43:58 > 0:44:02Two of these plates - the Nazca and the South American -
0:44:02 > 0:44:06have thrown up the Andes as they've crashed together, deep below us.
0:44:08 > 0:44:12Peru suffers from serious earthquakes every few years.
0:44:12 > 0:44:18They're caused by that Nazca plate pushing underneath the South American one.
0:44:18 > 0:44:20As the plates collide, friction makes them stick,
0:44:20 > 0:44:24the pressure builds until suddenly, they slip.
0:44:24 > 0:44:26The result is earthquakes, landslides
0:44:26 > 0:44:29and terrible devastation.
0:44:33 > 0:44:37The Incas knew all about the geological risks of the region.
0:44:37 > 0:44:41And while there's little they could do about a mountain shearing off,
0:44:41 > 0:44:45they had to design buildings capable of withstanding massive quakes.
0:44:51 > 0:44:54There's evidence of how they achieved this back here,
0:44:54 > 0:44:57overlooking the Inca village of Ollantaytambo.
0:44:57 > 0:45:02These monumental stones were in part an Inca response
0:45:02 > 0:45:05to the violent seismic activity that shook their empire.
0:45:05 > 0:45:07They're incredibly well carved -
0:45:07 > 0:45:10you can't even slip a coin or a piece of paper between them.
0:45:10 > 0:45:14And there's no need of mortar. As you go up the wall,
0:45:14 > 0:45:18the stones get smaller, which makes this structure incredibly stable.
0:45:18 > 0:45:23And if you look at where the joints meet, look, you can see they're staggered, not straight.
0:45:23 > 0:45:27It's like an interlocking jigsaw that minimises lines of weakness
0:45:27 > 0:45:32and all of this helps to make this construction earthquake-proof.
0:45:32 > 0:45:37Windows, doorways and most walls slope inwards
0:45:37 > 0:45:41to make them stronger and more flexible when a quake strikes.
0:45:41 > 0:45:46But how did they carve out these perfectly cut edges without steel?
0:45:47 > 0:45:52And how did they transport those huge stone blocks without the wheel?
0:45:52 > 0:45:56Apparently, there are some clues at the bottom of this ramp.
0:45:58 > 0:46:01And on hand to tell me more, historian Peter Frost.
0:46:01 > 0:46:03Hi, Peter, so what we got here?
0:46:03 > 0:46:07- It's a tired stone, as they call them here.- What's a tired stone?
0:46:07 > 0:46:11It's a stone that never made it from the quarries to the construction site.
0:46:11 > 0:46:14So does this give us an idea on how it was carved?
0:46:14 > 0:46:20Yeah, we have to get on the top really to see what they've been doing here. Hang on.
0:46:22 > 0:46:27- You see these pockmarks all over the surface of this stone? - Yes - to me these aren't natural.
0:46:27 > 0:46:31No, those are the tell-tale signs of Inca use of hammer stones.
0:46:31 > 0:46:35- This is an Inca hammer stone made of hematite. - Oh, iron ore. Wow, its heavy.
0:46:35 > 0:46:37Very heavy, very hard,
0:46:37 > 0:46:41and very effective in carving away the surface of a softer stone.
0:46:41 > 0:46:45- So they would just peck, peck, peck, rock on rock?- That's it.
0:46:45 > 0:46:49- Must have taken them absolute ages. - Not as much as you might think -
0:46:49 > 0:46:53because there are people who've duplicated this work in Inca quarries,
0:46:53 > 0:46:57that in fact it doesn't take as long as you'd imagine.
0:46:57 > 0:47:01I mean, this is enormous, how did they actually transport it?
0:47:01 > 0:47:05They were coming across open country here from the quarries
0:47:05 > 0:47:08and if you have enough people and enough rope, you can do it.
0:47:08 > 0:47:12And the Incas did have this huge reserve of manpower,
0:47:12 > 0:47:14they were never short of people.
0:47:14 > 0:47:16Couldn't they have used cattle to pull it?
0:47:16 > 0:47:19- They didn't have cattle. - They didn't have cattle?
0:47:19 > 0:47:24Peter, I'm gonna give you back your hammer stone and say thank you once again.
0:47:24 > 0:47:26That was very useful, thanks.
0:47:26 > 0:47:31- I'll gonna finish carving this stone. - Are you? Well, don't ask me to drag it up the hill. Bye!
0:47:31 > 0:47:35Although the Incas had been dealt a truly harsh hand by geology,
0:47:35 > 0:47:40they were ingenious enough to fight back and thrive.
0:47:41 > 0:47:44But theirs is a story with a bitter twist.
0:47:45 > 0:47:49To show you what it was, I've come to the Inca capital, Cuzco.
0:47:56 > 0:47:59This was a centre of Inca power and wealth.
0:47:59 > 0:48:04From here, the Inca emperors, believed to be the divine descendents of the sun,
0:48:04 > 0:48:06ruled their vast empire.
0:48:10 > 0:48:12Cuzco is a bustling, modern city,
0:48:12 > 0:48:16but there are still traces of its glory under the Incas.
0:48:18 > 0:48:21Some streets are flanked by extraordinary foundation walls
0:48:21 > 0:48:25that have withstood centuries of earthquakes.
0:48:29 > 0:48:32The proud Inca empire was built supremely
0:48:32 > 0:48:35to cope with the challenges of its geological setting.
0:48:35 > 0:48:40Here were a people who knew how to farm the mountains, administer a rugged terrain
0:48:40 > 0:48:44and build magnificent roads, storehouses and buildings
0:48:44 > 0:48:47to withstand the shaking of the earth.
0:48:47 > 0:48:50They might have thought, what could possibly go wrong?
0:48:54 > 0:48:58In the end, of course, their undoing was down to a product
0:48:58 > 0:49:01of the giant geological cooking pot beneath their feet...
0:49:01 > 0:49:03gold.
0:49:03 > 0:49:09It's hard to believe that these shiny precious trinkets started off as a metal-rich stew
0:49:09 > 0:49:14injected by superheated waters up into the hearts of mountains
0:49:14 > 0:49:17and later liberated by eroding rivers
0:49:17 > 0:49:22to form particles or nuggets of pure gold.
0:49:32 > 0:49:37The Incas loved gold, not as money, but for making beautiful objects.
0:49:37 > 0:49:43For them, it only took on value when crafted into ceremonial jewellery, figurines
0:49:43 > 0:49:46and adornments for tombs and temples.
0:49:51 > 0:49:58In 1532, Francisco Pizarro and his Spanish conquistadors arrived in Peru
0:49:58 > 0:50:00and they came in search of gold.
0:50:05 > 0:50:07While the Incas had mastered the landscape,
0:50:07 > 0:50:10they were unprepared for the threat of the Spanish.
0:50:10 > 0:50:14Within a few years, they were a conquered people,
0:50:14 > 0:50:16their glory extinguished.
0:50:16 > 0:50:20But one extraordinary treasure escaped the Spanish
0:50:20 > 0:50:22and it's not here in Cuzco.
0:50:26 > 0:50:30The climax of my geological journey is an archaeological treasure
0:50:30 > 0:50:37that lies at the end of a three-day hike, or from Cuzco, a four-hour train ride.
0:50:37 > 0:50:41Recent discoveries at Machu Picchu have given us a new insight
0:50:41 > 0:50:45into the true nature of the Inca relationship with the mountains.
0:50:45 > 0:50:49All the trains go to Machu Picchu here.
0:50:49 > 0:50:53'Archaeologist and explorer Dr Gary Zeigler is coming with me.'
0:50:53 > 0:50:55This is quite a crowd, isn't it?
0:50:55 > 0:51:00- Something like 500,000, I understand, go to Machu Picchu.- 500,000?
0:51:00 > 0:51:02Can you believe that? That's a year.
0:51:02 > 0:51:07'In the last few years, Gary's expeditions have uncovered two major Inca sites
0:51:07 > 0:51:12'once hidden in this region. He's a real-life Indiana Jones.'
0:51:16 > 0:51:23It was here, 85 years ago, that another American made one of the finds of the century.
0:51:23 > 0:51:27- So tell me about the discovery of Machu Picchu. - Oh, it's a wonderful story.
0:51:27 > 0:51:32Hiram Bingham, an intrepid American explorer in the year 1911,
0:51:32 > 0:51:36was travelling down the Urabamba River Valley looking for ruins
0:51:36 > 0:51:41and he stopped at a small place there, what's below Machu Picchu now.
0:51:41 > 0:51:47There was a family actually farming on one of the terraces at Machu Picchu.
0:51:47 > 0:51:53- He offered a reward, they took him up and he found the site. - So it's easy?- Piece of cake.
0:51:53 > 0:51:58- So how do you do it today? - Well, we tried hi-tech, we tried satellite imagery
0:51:58 > 0:52:02we tried thermal imaging from an aircraft,
0:52:02 > 0:52:05but it's all come down to swinging a machete.
0:52:05 > 0:52:07- Old style.- That's right.
0:52:09 > 0:52:12Gary is going to show me something in Machu Picchu
0:52:12 > 0:52:16that these tourists won't find in their guidebooks.
0:52:19 > 0:52:22There's something hidden in its design,
0:52:22 > 0:52:27an ancient geological code that's only now being unlocked.
0:52:47 > 0:52:51High above the Urabamba River, deep in cloud forest,
0:52:51 > 0:52:54lies breathtaking Machu Picchu.
0:53:04 > 0:53:06Wow, look at this.
0:53:07 > 0:53:08Is this not fantastic?
0:53:08 > 0:53:11This is the classic view, isn't it?
0:53:11 > 0:53:13- It is.- The clouds sweeping in over.
0:53:13 > 0:53:18It really captures the mystery and the romance of it.
0:53:18 > 0:53:21- Can you imagine how it looked in Inca times?- I haven't a clue.
0:53:21 > 0:53:24Imagine the thatched roofs covering everything,
0:53:24 > 0:53:27imagine these walls being brilliantly white
0:53:27 > 0:53:30with decorative plants and flowers around.
0:53:30 > 0:53:34- It must have been ablaze with colour.- Undoubtedly.
0:53:39 > 0:53:44Until recently, the importance of the mountains that embrace Machu Picchu
0:53:44 > 0:53:47has not been fully appreciated.
0:53:47 > 0:53:52It's these peaks that are the key to deciphering the Incas' geological code.
0:53:54 > 0:53:58Everywhere Gary takes me, he points out carved rocks.
0:53:58 > 0:54:00He's picking out replica stones,
0:54:00 > 0:54:04designed to echo the shapes of the mountains behind them.
0:54:10 > 0:54:12I'm starting to see replica mountains everywhere.
0:54:15 > 0:54:21Well, look at this. This is one of the best replication stones I know of at Machu Picchu.
0:54:21 > 0:54:23Look carefully at the shape of the rock,
0:54:23 > 0:54:25look at the two arms coming off of it,
0:54:25 > 0:54:28It seems to closely represent the mountain in the background,
0:54:28 > 0:54:31which is Cerro Yanatin.
0:54:31 > 0:54:35And that sloping bit at the back is the sloping back wall of the peak.
0:54:35 > 0:54:38Exactly - as close to the canyon on the right as you can get.
0:54:38 > 0:54:40- That's amazing.- It's amazing.
0:54:40 > 0:54:45They certainly intended to make a replication of the mountain in the background.
0:54:45 > 0:54:50What this suggests then is that Yanatin was something important in mountain worship
0:54:50 > 0:54:53at least to this part of the site and people passing by here,
0:54:53 > 0:54:57and so they took the boulder, they enshrined or made a roadside shrine
0:54:57 > 0:54:59of a replica of the peak behind.
0:55:03 > 0:55:06'Inca religion venerated not only mountains,
0:55:06 > 0:55:08'but boulders and rock formations.
0:55:10 > 0:55:15'Their architecture sought to work in harmony with the surrounding stone.'
0:55:15 > 0:55:17And here's this great carved stairway.
0:55:17 > 0:55:20- This is all rock?- All solid rock. - Wow.
0:55:20 > 0:55:22Carved out of the native bedrock.
0:55:24 > 0:55:28As we come up on top of the highest point here,
0:55:28 > 0:55:31there's something I'd like to show you that's fantastic.
0:55:35 > 0:55:37Look across the plaza,
0:55:37 > 0:55:42look at this wonderful example of native rock blended into the construction.
0:55:42 > 0:55:46- It's beautiful.- That's one of the finest examples of Inca architecture
0:55:46 > 0:55:48in the entire Inca empire.
0:55:48 > 0:55:52Fantastic, how they've blended that in there.
0:55:56 > 0:55:59Since Hiram Bingham's rediscovery of Machu Picchu,
0:55:59 > 0:56:05sun worship and solstice ritual were believed to be the main religious rites here.
0:56:05 > 0:56:09After all, we know the Emperor claimed descent and authority from the Sun God.
0:56:09 > 0:56:13But the new focus on the site's geology has changed that.
0:56:13 > 0:56:19Now, Machu Picchu appears more like an altar to the rocks.
0:56:19 > 0:56:22Iain, here we are. This is my favourite place
0:56:22 > 0:56:26and probably the most sacred point, most important point of Machu Picchu.
0:56:26 > 0:56:32And it's interesting that Bingham identified this or named it the Intihuatana.
0:56:32 > 0:56:36Intihuatana means, in some sort of description,
0:56:36 > 0:56:39"hitching post of the sun". Others have called it a sundial.
0:56:39 > 0:56:44But of course, most of what Hiram Bingham established in his conclusions
0:56:44 > 0:56:46has since been reinterpreted.
0:56:46 > 0:56:48- A bit too imaginative, was he? - Exactly.
0:56:48 > 0:56:52We now think that the stone is more of a focal point.
0:56:52 > 0:56:56It seems to be a replication of Huaynu Pichhu mountain
0:56:56 > 0:56:59and because it's the highest point in Machu Picchu,
0:56:59 > 0:57:04it represents Huaynu Pichhu as the protective deity of Machu Picchu, the city.
0:57:04 > 0:57:08Yeah. It looks obvious, but also its just a beautiful rock, isn't it?
0:57:08 > 0:57:11It's exquisitely carved. It's like a piece of art.
0:57:11 > 0:57:13It certainly is. It's Inca art.
0:57:13 > 0:57:16Inca art, yeah. Geology and art.
0:57:17 > 0:57:19Fabulous.
0:57:28 > 0:57:31For me, it doesn't get any better.
0:57:31 > 0:57:35I've learned that the Inca story is inextricably woven into the rocks.
0:57:35 > 0:57:39These rugged lands, the climate, the gold - all were products
0:57:39 > 0:57:44of geological forces at work beneath the feet of these great people.
0:57:44 > 0:57:46That they built such a successful empire
0:57:46 > 0:57:51was down to their deep understanding of this unique natural landscape.
0:57:56 > 0:57:59The secrets of Machu Picchu that have recently been revealed
0:57:59 > 0:58:03show that the Incas not only understood these magnificent mountains,
0:58:03 > 0:58:08they worshipped them in a profound, and to me, even moving way.
0:58:08 > 0:58:11And what I've discovered from my journey through modern Peru
0:58:11 > 0:58:14is that this respect and veneration for the Andes
0:58:14 > 0:58:17is still a vital part of life here today.
0:58:53 > 0:58:55Subtitles by Red Bee Media Ltd
0:58:55 > 0:58:58Email subtitling@bbc.co.uk