0:00:03 > 0:00:07More than half of us now live in cities,
0:00:07 > 0:00:09and more of us are moving in.
0:00:09 > 0:00:14By 2050, two-thirds of the planet will be city dwellers.
0:00:14 > 0:00:16There's people going this way, people going that way.
0:00:16 > 0:00:18It's bonkers!
0:00:18 > 0:00:24We're exploring four iconic cities in all four corners of the world.
0:00:24 > 0:00:27This cycle rickshaw is coming the wrong way towards us.
0:00:27 > 0:00:29These are places bursting with life.
0:00:31 > 0:00:35Crowded, chaotic and complicated,
0:00:35 > 0:00:37they're also under pressure.
0:00:37 > 0:00:39HORNS BLARE
0:00:39 > 0:00:40All right, mate.
0:00:42 > 0:00:44We're going behind the scenes...
0:00:45 > 0:00:49..to uncover the hidden systems and armies of people
0:00:49 > 0:00:52running some of the greatest cities on Earth.
0:00:54 > 0:00:57This time, we're in Mexico City.
0:00:57 > 0:01:01A sprawling megalopolis, fuelled by optimism and enterprise.
0:01:03 > 0:01:04We're going to show you
0:01:04 > 0:01:07how this often makeshift and haphazard city works.
0:01:08 > 0:01:12Uncovering the incredible story of how it survives
0:01:12 > 0:01:13its many daily battles.
0:01:15 > 0:01:19Historian Dan Snow finds out what it's like
0:01:19 > 0:01:22to build big in a deadly earthquake zone.
0:01:22 > 0:01:25I'm feeling more confident about Mexico City's tallest building.
0:01:25 > 0:01:27Even if there's an earthquake, we're going be fine.
0:01:27 > 0:01:29You're going to be perfectly safe.
0:01:29 > 0:01:33Journalist Ade Adepitan looks for new sources of water
0:01:33 > 0:01:36in one of the world's thirstiest cities.
0:01:36 > 0:01:37That looks clean to me.
0:01:37 > 0:01:39Yeah, it is.
0:01:40 > 0:01:44It's fantastic. I'm so impressed, I am.
0:01:45 > 0:01:47And I'm Anita Rani.
0:01:47 > 0:01:51I'll be learning how they're trying to stop this massive megacity
0:01:51 > 0:01:53from drowning in its own waste.
0:01:53 > 0:01:55Oh, it's a sofa!
0:01:55 > 0:01:57There's a whole dashboard here.
0:01:57 > 0:01:59I mean, it's horrendous,
0:01:59 > 0:02:02but a vital part of any city.
0:02:02 > 0:02:05Join us for the adventure of a lifetime
0:02:05 > 0:02:07in The World's Busiest Cities.
0:02:22 > 0:02:24Mexico City -
0:02:24 > 0:02:27home to nearly 22 million people.
0:02:27 > 0:02:31And where better to start than in its beating heart - the streets?
0:02:33 > 0:02:37- Now this is a proper locals' market, isn't it?- Yeah, exactly.
0:02:37 > 0:02:41So, this is where you're going to get absolutely everything you need.
0:02:41 > 0:02:42Oh, my God.
0:02:43 > 0:02:47Street food is almost a religion here -
0:02:47 > 0:02:50a mix of the cultures that built this city.
0:02:50 > 0:02:52DAN LAUGHS
0:02:52 > 0:02:54Amazing. We are in the home of the chilli.
0:02:54 > 0:02:55I know.
0:02:55 > 0:02:59VOICEOVER: This is one of 1,000 tianguis, or open-air markets,
0:02:59 > 0:03:02that have been here since the city began.
0:03:02 > 0:03:05Even the name dates back to the Aztec Empire.
0:03:06 > 0:03:08- Right, you're going to try that. - I...
0:03:08 > 0:03:10- OK!- OK.
0:03:10 > 0:03:13VOICEOVER: When the Spanish arrived in the 16th century,
0:03:13 > 0:03:17they called this food antojitos, or "little cravings".
0:03:17 > 0:03:22It's still a big part of how this informal city is fed.
0:03:22 > 0:03:23Gracias, muchas gracias.
0:03:23 > 0:03:26Street food is what it's all about in Mexico, Dan.
0:03:26 > 0:03:28That is so...
0:03:28 > 0:03:31It's terrifying. Go on, you go first.
0:03:31 > 0:03:33She orders it, she makes me try it -
0:03:33 > 0:03:34that's how this relationship works!
0:03:34 > 0:03:36- Gentleman first.- Oh, God.
0:03:36 > 0:03:38Let's hope it's better than it looks.
0:03:40 > 0:03:42Oh!
0:03:42 > 0:03:44How is it? I'm going to try it.
0:03:44 > 0:03:47- Delicious.- Is it really hot? - It's really hot.
0:03:49 > 0:03:51- Crazy woman! - Have I put too much chilli in it?
0:03:52 > 0:03:54Mm! That chilli is a killer.
0:03:54 > 0:03:56Thanks for the chilli, yeah.
0:03:56 > 0:03:58You can't come to Mexico and not have chilli!
0:04:00 > 0:04:04Home to an incredible one-fifth of Mexico's total population,
0:04:04 > 0:04:08this is a city that has come to define urban sprawl,
0:04:08 > 0:04:12with self-built homes clustered on its scattered hillsides.
0:04:13 > 0:04:18These colourful markets are where people come together.
0:04:18 > 0:04:21What I love about this place is, already, it can only be Mexico,
0:04:21 > 0:04:23you couldn't be anywhere else in the world - what people are eating,
0:04:23 > 0:04:25what they're wearing, what they look like.
0:04:25 > 0:04:27Even though it's so close to the United States,
0:04:27 > 0:04:29you expect American culture to be down here.
0:04:29 > 0:04:32In fact, it's just brilliantly vibrant, Mexican...
0:04:32 > 0:04:34- And so distinct. - Yeah, it's so distinct.- Yeah.
0:04:34 > 0:04:35And everybody's sitting down and eating.
0:04:35 > 0:04:37There's food stalls every five yards.
0:04:40 > 0:04:43Mexico City is one of the most challenging
0:04:43 > 0:04:45urban environments on the planet.
0:04:47 > 0:04:51It's grown at a staggering pace and is struggling to cope.
0:04:51 > 0:04:53HORNS BLARE
0:04:55 > 0:04:58It's crowded, it's congested...
0:05:00 > 0:05:03..there are problems with water and sewerage,
0:05:03 > 0:05:08and this haphazard city sits in a major earthquake zone,
0:05:08 > 0:05:13where parts of it are sinking around ten centimetres every year.
0:05:13 > 0:05:16VOICEOVER: But, sitting here, you'd never know it.
0:05:16 > 0:05:17I think it's interesting,
0:05:17 > 0:05:20because it is a city with massive ecological and other problems,
0:05:20 > 0:05:22and yet people don't seem very fussed about it.
0:05:22 > 0:05:25They're just getting on with it. They're enjoying it.
0:05:25 > 0:05:27And we're in the capital city, and yet this feels like
0:05:27 > 0:05:29we could be in, sort of, rural Mexico somewhere,
0:05:29 > 0:05:31some local market.
0:05:34 > 0:05:35See, Dan?
0:05:35 > 0:05:37People might think that this is some sort of cliche,
0:05:37 > 0:05:38but it's real, it happens.
0:05:38 > 0:05:40People just turn up and start playing trumpet.
0:05:43 > 0:05:47We're going to find out what really makes this megacity tick
0:05:47 > 0:05:51and experience the hidden systems and strength of spirit
0:05:51 > 0:05:56that allow it to defy everything its nearly 22 million inhabitants
0:05:56 > 0:05:59and Mother Nature can throw at it.
0:05:59 > 0:06:02There's no mistaking it now, Dan. We are in Mexico.
0:06:05 > 0:06:07- Whoo!- Wahey!
0:06:10 > 0:06:15Mexico City sits right at the centre of the country it serves as capital,
0:06:15 > 0:06:21high on a plateau, at 2,240 metres above sea level.
0:06:21 > 0:06:25Founded on a lake that was drained by the Spanish conquistadors,
0:06:25 > 0:06:28the city exploded in the 20th century,
0:06:28 > 0:06:32spilling over from its historic core into a metropolitan area
0:06:32 > 0:06:36now stretching over nearly 1,000 square miles -
0:06:36 > 0:06:39the largest in the entire Western Hemisphere.
0:06:43 > 0:06:47We're splitting up to explore this epic sprawl.
0:06:47 > 0:06:50While Anita and Dan travel deeper into the city,
0:06:50 > 0:06:53I'm heading to the suburb of Neza
0:06:53 > 0:06:58to find out just how this city grew and grew and grew.
0:07:09 > 0:07:11Now, I've come here because this place
0:07:11 > 0:07:13has got a really fascinating history.
0:07:13 > 0:07:16Now, I've been told that all these colourful houses around here
0:07:16 > 0:07:19have been self-built, brick by brick, by the residents.
0:07:19 > 0:07:20I haven't been here that long,
0:07:20 > 0:07:24and this place is already giving off this really interesting vibe.
0:07:24 > 0:07:27Now, I'm going to meet one of the families that've been here
0:07:27 > 0:07:29since the early days,
0:07:29 > 0:07:31just to find out a little bit more about this place.
0:07:34 > 0:07:37If you need somewhere to live in Mexico City,
0:07:37 > 0:07:38you build it yourself.
0:07:38 > 0:07:42Incredibly, more than half the architecture here
0:07:42 > 0:07:44is built without regulations
0:07:44 > 0:07:47ensuring basic construction standards.
0:07:47 > 0:07:50- Hola.- Hola. Buen dia. - Buen dia.
0:07:50 > 0:07:52Hola. Benito...
0:07:52 > 0:07:55- VOICEOVER:- Benito Perez and his mother-in-law, Gloria Lopez,
0:07:55 > 0:07:58have lived in this house for decades.
0:07:59 > 0:08:01IN SPANISH:
0:08:39 > 0:08:42In Mexico City, more than 60% of people
0:08:42 > 0:08:45live in areas known as colonias populares -
0:08:45 > 0:08:48informal, unregulated settlements.
0:08:50 > 0:08:51It's how Neza started.
0:08:59 > 0:09:01Oh, it's just amazing.
0:09:01 > 0:09:04I wouldn't know where to start when it comes to building a house.
0:09:04 > 0:09:06But, you know, these people, they're just so...
0:09:06 > 0:09:08They're so motivated.
0:09:17 > 0:09:18Wow.
0:09:19 > 0:09:22In this house, there's 22 people that live here,
0:09:22 > 0:09:25and four generations of their family,
0:09:25 > 0:09:26which is incredible.
0:09:38 > 0:09:40You know, it's like anywhere in the world, man -
0:09:40 > 0:09:42you want to make your house a castle, don't you?
0:09:44 > 0:09:47- VOICEOVER:- I'm surprised to discover that the family
0:09:47 > 0:09:48don't just live here -
0:09:48 > 0:09:52Benito also runs his shoe business from the house.
0:09:59 > 0:10:02Look at that. He's just making a shoe...
0:10:03 > 0:10:05..right in front of my very eyes.
0:10:06 > 0:10:09- VOICEOVER:- Benito tells me that businesses like his
0:10:09 > 0:10:12are a common feature in homes across the city.
0:10:12 > 0:10:15Households, they'll either be selling shoes,
0:10:15 > 0:10:17they'll be making something, and then they'll take it
0:10:17 > 0:10:20to the tianguis, the local market, the portable market,
0:10:20 > 0:10:22to earn money for their families.
0:10:22 > 0:10:25So the house is more than just a house.
0:10:25 > 0:10:28It's a business, it's everything for them.
0:10:29 > 0:10:32- VOICEOVER:- I feel humbled that the family has invited me
0:10:32 > 0:10:34to stay for lunch.
0:10:34 > 0:10:37In Mexico, food is a serious business.
0:10:41 > 0:10:44- VOICEOVER:- It's my chance to meet the rest of the family,
0:10:44 > 0:10:46including Benito's wife, Sandra.
0:10:46 > 0:10:48You're going to speak English to me, yes?
0:10:48 > 0:10:50Si. Poquito!
0:10:50 > 0:10:51THEY LAUGH
0:10:53 > 0:10:56- VOICEOVER:- There's Grandad Bernabe, who built this house,
0:10:56 > 0:10:58Benito's daughter Lupita,
0:10:58 > 0:11:00and the rest of the family.
0:11:03 > 0:11:07This is really cool, actually, to have traditional Mexican food
0:11:07 > 0:11:09in a house that was built by this family.
0:11:09 > 0:11:12I mean, you can't get more authentic than that, can you?
0:11:12 > 0:11:13They're going to pray.
0:11:24 > 0:11:25- Amen.- Aproveche. - Gracias.
0:11:30 > 0:11:32Oh...!
0:11:34 > 0:11:36Si?
0:11:37 > 0:11:40- VOICEOVER:- Benito wants to show me photos from the early 1970s,
0:11:40 > 0:11:43taken when Grandad Bernabe was building the house.
0:12:01 > 0:12:03THEY LAUGH
0:12:08 > 0:12:10Wow. Benito learned from his father-in-law.
0:12:10 > 0:12:13But his father-in-law learned from watching other people.
0:12:13 > 0:12:17That was it, you know. Just watched other people and decided,
0:12:17 > 0:12:19"I'm going to create this, my dream."
0:12:19 > 0:12:20It's incredible.
0:12:24 > 0:12:28Just 40 years ago, Neza was on the fringes of the sprawl.
0:12:28 > 0:12:31Now, more than 1 million people live here,
0:12:31 > 0:12:34and the settlement has been absorbed into Mexico City.
0:12:34 > 0:12:37It's a testament to the spirit of its citizens.
0:12:41 > 0:12:43Que paso? Que tal?
0:12:43 > 0:12:45It's a lot of character going on in this place.
0:12:53 > 0:12:56As people build houses further and further out,
0:12:56 > 0:13:00their journeys into work get longer and longer.
0:13:00 > 0:13:02I've been thrown in at the deep end,
0:13:02 > 0:13:05trying to figure out the daily commute.
0:13:05 > 0:13:06HORN BLARES
0:13:06 > 0:13:08All right, mate.
0:13:10 > 0:13:12Buses here are cheap and plentiful.
0:13:12 > 0:13:16In fact, this is one of the biggest bus systems in the world,
0:13:16 > 0:13:19but it's also a bit of a mystery.
0:13:20 > 0:13:22It's incredibly chaotic.
0:13:22 > 0:13:24I have no idea what's happening.
0:13:24 > 0:13:26But they're all going somewhere,
0:13:26 > 0:13:28and all the locals seem to know which one to get.
0:13:34 > 0:13:37These little buses are known as peseros.
0:13:37 > 0:13:40They got their name because they used to charge one peso -
0:13:40 > 0:13:41that's just 4p.
0:13:43 > 0:13:45They account for an incredible 60%
0:13:45 > 0:13:49of all journeys made by commuters every day.
0:13:49 > 0:13:53But there are no bus stops and no marked routes.
0:13:54 > 0:13:59How do you know? How do you know which one to get?
0:13:59 > 0:14:02Peseros are an unofficial system that's grown with demand.
0:14:02 > 0:14:08They're unregulated, unlicensed, and, crucially, unmapped.
0:14:08 > 0:14:11I'm going to need some help to find my way.
0:14:11 > 0:14:13- Hola, Christian.- Hi. - How are you doing?
0:14:13 > 0:14:16VOICEOVER: Enterprising Mexicans like Christian Guerrero
0:14:16 > 0:14:19are trying to bring order to the chaos.
0:14:19 > 0:14:22So, how do you know what bus you need to get?
0:14:22 > 0:14:24Well, mostly, you ask the people around.
0:14:24 > 0:14:28Like, either your family or your friends.
0:14:28 > 0:14:31So it's mostly, like, general knowledge in the population.
0:14:31 > 0:14:33- Local, Mexican City knowledge? - Exactly.
0:14:35 > 0:14:37VOICEOVER: On average, Mexico City residents
0:14:37 > 0:14:40spend about two-and-a-half hours a day commuting...
0:14:40 > 0:14:42Thank you.
0:14:42 > 0:14:44..much of it on buses like this.
0:14:46 > 0:14:47And we're on.
0:14:51 > 0:14:53How many peseros are there in Mexico City?
0:14:53 > 0:14:55Around 50,000.
0:14:55 > 0:14:58- Yeah.- 50,000 of these buses?
0:14:58 > 0:15:00Yeah.
0:15:00 > 0:15:03It's getting busy. Coming on, ladies.
0:15:03 > 0:15:05VOICEOVER: Christian wants to modernise
0:15:05 > 0:15:07the 40-year-old pesero system
0:15:07 > 0:15:10and make it easier for passengers to use.
0:15:10 > 0:15:12He's developed a smartphone app
0:15:12 > 0:15:14that aims to map the entire network
0:15:14 > 0:15:17with the help of passengers riding the routes.
0:15:17 > 0:15:20The idea is that you would use your phone
0:15:20 > 0:15:23in order to, first of all, take a picture
0:15:23 > 0:15:25of the sign in the front of the bus,
0:15:25 > 0:15:29and that picture would tell us which route it was.
0:15:29 > 0:15:31So once you took the picture,
0:15:31 > 0:15:35you would use your GPS and start mapping.
0:15:35 > 0:15:37Do you know how many miles it covers?
0:15:37 > 0:15:3952,000km.
0:15:39 > 0:15:43So about 32,000 miles.
0:15:43 > 0:15:45- Yeah. Exactly.- That's a lot.
0:15:45 > 0:15:47And it's an ongoing process.
0:15:47 > 0:15:48Yeah, it's growing and growing.
0:15:51 > 0:15:53It's a very smart solution -
0:15:53 > 0:15:56crowd-sourcing routes so they can be made available
0:15:56 > 0:15:58to anyone with a smartphone.
0:15:58 > 0:16:01This is a fusion of the old and the new.
0:16:03 > 0:16:06In 40, 50 years, nobody has done anything
0:16:06 > 0:16:09in order to let this system work correctly,
0:16:09 > 0:16:14so if we don't do anything, this city will stop moving.
0:16:14 > 0:16:19And you're having to come up with apps and solutions to improve it,
0:16:19 > 0:16:21- to bring into the 21st century. - Yeah.
0:16:23 > 0:16:26The peseros are an integral part of Mexico City.
0:16:27 > 0:16:29They're typical of this place -
0:16:29 > 0:16:33an informal and slightly haphazard solution to an urban problem.
0:16:36 > 0:16:40Where else can you be serenaded while waiting for the bus home?
0:16:46 > 0:16:48I love Mexico.
0:16:48 > 0:16:51Standing on the side of a dual carriageway,
0:16:51 > 0:16:53these chaps get off and start serenading me.
0:17:00 > 0:17:03Yes, gentlemen. Muchas gracias.
0:17:03 > 0:17:05- Have a nice evening. - Thank you so much.
0:17:05 > 0:17:08That was so wonderful, they were actually really good.
0:17:08 > 0:17:10Now which of these peseros do I get home?
0:17:12 > 0:17:13Do I get this one?
0:17:13 > 0:17:15I have no idea. No idea.
0:17:15 > 0:17:16Don't know where I am.
0:17:23 > 0:17:25While Anita gets lost on the buses,
0:17:25 > 0:17:29I'm off to discover what made this city great in the first place.
0:17:32 > 0:17:35This is one of the oldest continuously inhabited settlements
0:17:35 > 0:17:36in the Western Hemisphere.
0:17:38 > 0:17:42The modern city might be an assault on the senses,
0:17:42 > 0:17:46but you don't have to go far to see its ancient roots.
0:17:46 > 0:17:50Everything here in Mexico City is a product of its unique past,
0:17:50 > 0:17:54and there are places within the city where the past and the modern
0:17:54 > 0:17:55are all jumbled in right next to each other.
0:17:55 > 0:17:59Like here, modern apartment blocks, big, busy motorway,
0:17:59 > 0:18:02but right next to it is this astonishing historical site -
0:18:02 > 0:18:04the Place of the Three Cultures.
0:18:04 > 0:18:06And those three cultures are, in the middle, the remains
0:18:06 > 0:18:09of an old step pyramid from the Aztec period -
0:18:09 > 0:18:11the Aztecs, one of the great civilisations of world history.
0:18:11 > 0:18:13Then the Spanish arrived in the 16th century,
0:18:13 > 0:18:15they literally dismantled those temples
0:18:15 > 0:18:17and built churches like that right on top of them.
0:18:17 > 0:18:19What a statement of colonial control.
0:18:19 > 0:18:20And then there's modern buildings
0:18:20 > 0:18:23from Mexico's post-independence period as well.
0:18:27 > 0:18:30The Aztecs settled here because there was water.
0:18:32 > 0:18:35They built their capital, Tenochtitlan,
0:18:35 > 0:18:39on a small island in the Lake of Texcoco.
0:18:39 > 0:18:43When the Spaniards arrived, they destroyed the island city
0:18:43 > 0:18:45and started to drain the lake.
0:18:46 > 0:18:49Where once was water, there's now sprawl.
0:18:50 > 0:18:53But there's one corner of this modern megacity
0:18:53 > 0:18:55where you can truly experience its history,
0:18:55 > 0:18:57and it's worth getting up early for.
0:19:07 > 0:19:09I've come now to the most beautiful place,
0:19:09 > 0:19:12a very far cry from the noise and bustle of Mexico City.
0:19:12 > 0:19:14The mist is coming off the water
0:19:14 > 0:19:16and the farmers are working the fields.
0:19:16 > 0:19:17It's beautiful.
0:19:19 > 0:19:21This is Xochimilco.
0:19:24 > 0:19:26Not far from the heart of the modern city,
0:19:26 > 0:19:31this working landscape is an insight into Mexico City's watery past.
0:19:33 > 0:19:37Early settlers built this ingenious system.
0:19:37 > 0:19:40Artificial islands, known as chinampas,
0:19:40 > 0:19:42on which to grow their crops.
0:19:49 > 0:19:53- VOICEOVER:- Lucio Usobiaga works with the farmers here
0:19:53 > 0:19:56to try and preserve the islands and their way of life.
0:19:58 > 0:20:00Did this used to extend right across the valley
0:20:00 > 0:20:02that Mexico City now sits in?
0:20:02 > 0:20:05Are we looking at the last remnants of these islands?
0:20:05 > 0:20:06Yeah, we are.
0:20:06 > 0:20:10In Mexico City, you know it's a basin,
0:20:10 > 0:20:13so it had five lakes.
0:20:13 > 0:20:19Right now, this is the last lake that we can really look at,
0:20:19 > 0:20:23and that it survives with some of its traditions.
0:20:23 > 0:20:26So this is the only place where you can come and get a feel
0:20:26 > 0:20:28for what life was like under the Aztecs?
0:20:28 > 0:20:30Yeah. Yeah, exactly.
0:20:30 > 0:20:35These chinampas were all made for agriculture.
0:20:35 > 0:20:36So they're all man-made?
0:20:36 > 0:20:38All man-made, yeah,
0:20:38 > 0:20:40more than a thousand years ago,
0:20:40 > 0:20:44even before the Aztecs came here and conquered the xochimilcas.
0:20:48 > 0:20:51Today, the chinampas are farmed as they've been for centuries,
0:20:51 > 0:20:55growing crops like maize, tomatoes and chilli peppers.
0:20:58 > 0:21:00This is lettuce.
0:21:00 > 0:21:02- VOICEOVER:- Lucio is taking me to meet
0:21:02 > 0:21:06a fourth-generation chinampero, Noe Coquis.
0:21:06 > 0:21:08Today, he's planting radishes.
0:21:08 > 0:21:11Noe, are your kids doing this farming as well?
0:21:11 > 0:21:14Is another generation of farmers being made?
0:21:25 > 0:21:28There'll be people farming here for generations to come.
0:21:38 > 0:21:40I really admire Noe's efforts
0:21:40 > 0:21:42to preserve the ancient farming methods.
0:21:44 > 0:21:48But Lucio wants to show me how these chinampas are being threatened
0:21:48 > 0:21:51by the rapidly sprawling city.
0:21:51 > 0:21:53We've come into a part of the chinampas now
0:21:53 > 0:21:54where we're seeing more houses.
0:21:54 > 0:21:57This one here built right onto the edge of the river bank.
0:21:57 > 0:22:00We can see illegal houses.
0:22:00 > 0:22:05It is not permitted to build houses in this natural protected area,
0:22:05 > 0:22:08but because of the housing demand,
0:22:08 > 0:22:14some people have no other alternative but to build them here.
0:22:14 > 0:22:17But this sums up the development of Mexico City over the centuries -
0:22:17 > 0:22:20people just constantly looking for new grounds,
0:22:20 > 0:22:22people moving here from elsewhere.
0:22:22 > 0:22:23There's a density of population here
0:22:23 > 0:22:26which means people need to find new ground to build.
0:22:26 > 0:22:29So do you think, if we come back here in 20 years' time,
0:22:29 > 0:22:31the chinampas may not be here?
0:22:31 > 0:22:37Well, I am hoping that there will be enough efforts and resources
0:22:37 > 0:22:39to prevent this from happening,
0:22:39 > 0:22:44and instead of seeing more houses, we'll start to plant more chinampas.
0:22:44 > 0:22:45Let's hope so.
0:22:50 > 0:22:53Mexico City was founded on water.
0:22:53 > 0:22:58The great irony is that, today, it now faces a water crisis.
0:23:00 > 0:23:03The draining of the lake system has left the city thirsty.
0:23:04 > 0:23:09It uses more water every day than any other city in the world.
0:23:11 > 0:23:13Millions are forced to get their water from trucks
0:23:13 > 0:23:17known as pipas, because they can't rely on the mains.
0:23:19 > 0:23:22I've come to a pipa depot in the borough of Tlalpan
0:23:22 > 0:23:25that sends out 200 trucks a day.
0:23:26 > 0:23:28It's pouring with rain,
0:23:28 > 0:23:31these trucks are filling up with gallons and gallons of water
0:23:31 > 0:23:34that's been piped down from the mountains,
0:23:34 > 0:23:38and they're going to be taken by these trucks
0:23:38 > 0:23:41back up to the mountains to be sold to the people.
0:23:43 > 0:23:45It's just crazy.
0:23:48 > 0:23:50Me llamo Ade.
0:23:50 > 0:23:53- VOICEOVER:- Uriel Canalez has been delivering water
0:23:53 > 0:23:55across the city for a few years.
0:24:17 > 0:24:20I'm amazed at what a precious and high-risk commodity
0:24:20 > 0:24:22water is in this city.
0:24:25 > 0:24:27Especially in the poorer neighbourhoods
0:24:27 > 0:24:29on the very edges of the sprawl.
0:24:31 > 0:24:35- VOICEOVER:- I've come to meet Rogelio Ramirez and his wife Sofia.
0:24:37 > 0:24:40They live in an area where water tankers are essential.
0:25:18 > 0:25:21I'm really surprised at the drastic measures
0:25:21 > 0:25:25that Rogelio has to take just to get the water that his family needs.
0:25:29 > 0:25:30Uh-huh.
0:25:39 > 0:25:41Yeah, it's just starting to rain.
0:25:41 > 0:25:44It's getting a little bit heavier and it's a good sign.
0:25:46 > 0:25:49This untreated water will be stored in a tank.
0:25:49 > 0:25:54The family won't drink it, but they do put it to good use.
0:26:21 > 0:26:22Wow, wow.
0:26:25 > 0:26:28Not a single drop of water is wasted.
0:26:42 > 0:26:47Families here can spend as much as 20% of their income on water.
0:26:49 > 0:26:54It's not that it doesn't rain here - it's just most of it is wasted.
0:26:57 > 0:27:00- VOICEOVER:- Enrique Lomnitz is working to find
0:27:00 > 0:27:02an affordable solution for everyone.
0:27:03 > 0:27:06These are, kind of, the forgotten people
0:27:06 > 0:27:07of the water situation in Mexico.
0:27:07 > 0:27:10Even though we're talking about millions of people.
0:27:10 > 0:27:13But that's crazy, when you get so much water in this area
0:27:13 > 0:27:17and you're in a city that has problems with water,
0:27:17 > 0:27:18why not use it?
0:27:18 > 0:27:20That's what we said.
0:27:20 > 0:27:21So we were like...
0:27:21 > 0:27:25It seemed to us like it was just a really obvious thing to do.
0:27:25 > 0:27:28So harvesting rainwater involves channelling the water
0:27:28 > 0:27:31that falls on your roof, with gutters or whatever,
0:27:31 > 0:27:34and putting it through some kind of treatment, and storing it.
0:27:35 > 0:27:39- VOICEOVER:- Enrique has been helping to install water capture systems
0:27:39 > 0:27:41in Tlalpan for the past seven years.
0:27:43 > 0:27:45Hola, hola.
0:27:45 > 0:27:48- VOICEOVER:- He's taken me to meet Eusebia Ventura.
0:27:48 > 0:27:51Like most of the people living on the edge of Mexico City,
0:27:51 > 0:27:53she has built her own home.
0:27:53 > 0:27:57So this is a 5,000-litre tank, and we put, as part of the project,
0:27:57 > 0:27:59the tank that's inside,
0:27:59 > 0:28:03and as she's grown the house, she's connected more roof,
0:28:03 > 0:28:05so now she has three rainwater harvesting systems.
0:28:07 > 0:28:11I'm pleased to hear that this system is already saving Eusebia money.
0:28:23 > 0:28:25So she makes something like 1,000 pesos a month
0:28:25 > 0:28:27and it would cost her 800 pesos to fill this.
0:28:37 > 0:28:39Whoa, here we go.
0:28:39 > 0:28:42Eusebia now captures and filters
0:28:42 > 0:28:4670,000 litres of rainwater every year.
0:28:46 > 0:28:49I want to taste the water from the sky.
0:28:49 > 0:28:52- Well, it looks clear. - Yep.- That looks clean to me.
0:28:52 > 0:28:53Yeah.
0:28:54 > 0:28:57So here's a glass of pure rainwater.
0:28:57 > 0:28:58Yes.
0:28:58 > 0:29:02And, you know, clean water in these areas is scarce
0:29:02 > 0:29:04and becoming a more scarce resource, no?
0:29:04 > 0:29:06- So it's like gold dust. - Yeah.
0:29:08 > 0:29:10It's perfectly clean water.
0:29:10 > 0:29:12Muy bien.
0:29:12 > 0:29:13Gracias.
0:29:13 > 0:29:14It's fantastic.
0:29:14 > 0:29:16- Si?- I'm so impressed.
0:29:16 > 0:29:17I am.
0:29:21 > 0:29:24Getting water into this megacity is one problem,
0:29:24 > 0:29:27but getting rid of it is quite another.
0:29:29 > 0:29:31I've come to Ecatepec to see a system
0:29:31 > 0:29:35that deals with one of Mexico City's dirtiest secrets.
0:29:36 > 0:29:40This is known as "agua negra" or black water.
0:29:40 > 0:29:42It's sewage waste water.
0:29:44 > 0:29:46And these days, it flows through a largely open sewer
0:29:46 > 0:29:48called the Grand Canal.
0:29:50 > 0:29:52VOICEOVER: Today, Carlos Teran and his team
0:29:52 > 0:29:55are cleaning the filters that keep the sewage flowing.
0:29:59 > 0:30:03I have no idea what pressing this button will dredge up.
0:30:04 > 0:30:06SHE EXCLAIMS
0:30:08 > 0:30:10Holy crap!
0:30:10 > 0:30:12It's a sofa.
0:30:13 > 0:30:15I mean, this is horrific.
0:30:15 > 0:30:16There's a whole dashboard here.
0:30:18 > 0:30:21Yeah. I mean, it's horrendous,
0:30:21 > 0:30:25but a vital part of any city, waste management.
0:30:25 > 0:30:27It's grim,
0:30:27 > 0:30:29but this is the reality of humans.
0:30:31 > 0:30:33That poor guy.
0:30:36 > 0:30:40This is one of 94 pumping stations
0:30:40 > 0:30:42along 7,000 miles of tunnels and pipes
0:30:42 > 0:30:45that form Mexico City's sewage system.
0:30:47 > 0:30:51The Grand Canal is now more than 100 years old.
0:30:51 > 0:30:53It used to flow downhill,
0:30:53 > 0:30:57using gravity to carry waste out of the city for treatment.
0:30:57 > 0:30:59But when Mexico City was drained,
0:30:59 > 0:31:02the clay lake bed started to collapse,
0:31:02 > 0:31:05forcing the canal up, not down.
0:31:05 > 0:31:10Engineers now battle gravity to pump the agua negra uphill,
0:31:10 > 0:31:13using pumping stations like this one.
0:31:13 > 0:31:16Parts of the city have sunk an astonishing 40 feet
0:31:16 > 0:31:18in the last century.
0:31:18 > 0:31:21These pumps have to work hard.
0:31:21 > 0:31:24So, Carlos, this is crucial, this is a crucial point.
0:31:36 > 0:31:39So if this didn't work, within three hours,
0:31:39 > 0:31:41the city would start to flood.
0:31:43 > 0:31:46The pumps are just a sticking plaster
0:31:46 > 0:31:48on Mexico City's sewage crisis.
0:31:48 > 0:31:50The Grand Canal was not designed to deal
0:31:50 > 0:31:54with the waste produced by nearly 22 million people
0:31:54 > 0:31:57in an ever-expanding megalopolis.
0:31:57 > 0:32:02So Mexico City is building big to solve its problem.
0:32:02 > 0:32:05This is the Emisor Oriente.
0:32:05 > 0:32:08It's an immense new waste water tunnel.
0:32:08 > 0:32:12What they're doing now is lowering the outer rings of the tunnel...
0:32:13 > 0:32:17..and each one of those weighs five tonnes,
0:32:17 > 0:32:21and it takes eight of them to build the entire outer wall,
0:32:21 > 0:32:23so that's 40 tonnes.
0:32:23 > 0:32:25This is serious engineering.
0:32:32 > 0:32:34This is it, we are descending 110 metres.
0:32:36 > 0:32:38And this lift is actually going a lot faster
0:32:38 > 0:32:40than I thought it would.
0:32:40 > 0:32:43This is like the journey to the centre of the Earth.
0:32:45 > 0:32:46Incredible!
0:32:48 > 0:32:50It's like we've entered the underworld.
0:32:50 > 0:32:57It's a lot darker, a lot cooler and there's a whole system at play here.
0:32:57 > 0:32:58Hola, Jose.
0:32:58 > 0:33:00- Hola, Anita.- Yes.
0:33:00 > 0:33:03VOICEOVER: Jose Lee Espinoza is the engineer in charge of this,
0:33:03 > 0:33:07one of Mexico City's biggest engineering projects.
0:33:07 > 0:33:08That was quite a descent.
0:33:08 > 0:33:12- Yes.- We are very, very deep...
0:33:12 > 0:33:14- Yes.- ..in this enormous tunnel.
0:33:14 > 0:33:15How many miles long is it going to be?
0:33:15 > 0:33:22More or less, 64km from Mexico City to the treatment plant.
0:33:22 > 0:33:25This is going to be one of the biggest tunnels in the world
0:33:25 > 0:33:27- when it's finished. - Yes, yes, I think so.
0:33:29 > 0:33:31We're making our way towards the front of the tunnel,
0:33:31 > 0:33:35where they're still drilling through solid rock.
0:33:35 > 0:33:40All of Mexico City's sewage and overflow of rainwater
0:33:40 > 0:33:43will be gushing through this enormous tunnel
0:33:43 > 0:33:45right where we are now.
0:33:45 > 0:33:46That's quite a thought!
0:33:48 > 0:33:51This new tunnel won't sink like the Grand Canal,
0:33:51 > 0:33:54because it's drilled so deep through hard rock.
0:33:54 > 0:33:58In fact, it will actually help Mexico City's sinking problem
0:33:58 > 0:34:02by stabilising the groundwater beneath the city.
0:34:03 > 0:34:06Finally, we reach the very front of the tunnel,
0:34:06 > 0:34:09as close as we can get to the huge drill
0:34:09 > 0:34:11that's boring the hole.
0:34:11 > 0:34:12The drill is just up ahead of us,
0:34:12 > 0:34:14it's nine metres in diameter
0:34:14 > 0:34:17and it's crunching away at the earth,
0:34:17 > 0:34:19getting rid of all those rocks.
0:34:19 > 0:34:21And as they're making space,
0:34:21 > 0:34:25they're laying those big chunks of concrete
0:34:25 > 0:34:27that go towards making the tunnel.
0:34:27 > 0:34:31How many kilometres are left to finish the whole tunnel?
0:34:31 > 0:34:34- 4km. - 4km left to do?
0:34:34 > 0:34:35- Yes.- And that will take how long?
0:34:35 > 0:34:37- Ten months.- In ten months,
0:34:37 > 0:34:44Mexico City will have its new massive sewage pipe.
0:34:44 > 0:34:46Yes.
0:34:51 > 0:34:54The more time you spend in this city,
0:34:54 > 0:34:58the more you realise how amazingly it fights Nature at every turn.
0:34:58 > 0:35:01Look at this extraordinary buildings here.
0:35:01 > 0:35:04Over the years, it's slowly subsiding at different speeds
0:35:04 > 0:35:07because the Spanish messed about with this place so much.
0:35:07 > 0:35:10They pumped out the groundwater, they reclaimed land for building,
0:35:10 > 0:35:13and, as a result, it's on very uncertain foundations.
0:35:20 > 0:35:23Check out that one there - that is leaning quite heavily over.
0:35:23 > 0:35:24It's all a bit haphazard.
0:35:26 > 0:35:31This subsidence has damaged the water and sewerage system.
0:35:32 > 0:35:36And it has another potentially deadly cost.
0:35:36 > 0:35:41Draining the lakes has dangerously changed the geology of Mexico City,
0:35:41 > 0:35:43leaving it vulnerable to earthquakes.
0:35:43 > 0:35:46Some of the most important parts
0:35:46 > 0:35:48of one of the biggest cities in the world
0:35:48 > 0:35:52now sit on a quivering pile of mud.
0:35:52 > 0:35:56The city is actually 200 miles from the nearest fault line
0:35:56 > 0:35:57off the Pacific coast,
0:35:57 > 0:36:00but the drained lake bed acts as an amplifier -
0:36:00 > 0:36:05seismic waves ripple and build as if shaking a bowl of jelly.
0:36:06 > 0:36:08Most cities have emergency services -
0:36:08 > 0:36:12police, ambulance and fire - but if you live here,
0:36:12 > 0:36:15you also need a 24-hour specialist search and rescue team...
0:36:17 > 0:36:19..like this elite unit.
0:36:19 > 0:36:21They're part of the Mexico City Police Force.
0:36:23 > 0:36:27They train every week, and today, they've agreed to show me
0:36:27 > 0:36:28how it's done.
0:36:28 > 0:36:32This is it. My childhood dream's come true.
0:36:32 > 0:36:35I'm going to get to pretend I'm a policeman for a minute.
0:36:38 > 0:36:39OK. Ready.
0:36:39 > 0:36:40Yeah.
0:36:42 > 0:36:44Right. Good.
0:36:44 > 0:36:46- VOICEOVER:- After an earthquake hits,
0:36:46 > 0:36:48it's critical to get victims out of collapsed buildings
0:36:48 > 0:36:50as quickly as possible.
0:36:50 > 0:36:53The team use drills to create a weak point in the wall,
0:36:53 > 0:36:56but then it's down to sheer brute force.
0:37:00 > 0:37:03That is exhausting. OK.
0:37:03 > 0:37:06- VOICEOVER:- I think it's time to hand over to a professional.
0:37:18 > 0:37:19Nice.
0:37:19 > 0:37:21That does give you a little bit of a sense
0:37:21 > 0:37:26of what it is like doing search and rescue in a huge city
0:37:26 > 0:37:28where you may have to do that time and time again,
0:37:28 > 0:37:30there's no end to the amount of buildings
0:37:30 > 0:37:32that could collapse, trapping people.
0:37:34 > 0:37:38The residents of the city have good reason to be fearful of earthquakes.
0:37:41 > 0:37:45In the early hours of the 19th of September 1985,
0:37:45 > 0:37:50Mexico City was devastated by a massive 8.1 magnitude earthquake.
0:37:51 > 0:37:56In just over a minute, around 100,000 houses were destroyed
0:37:56 > 0:38:00and 5 million residents were left without electricity
0:38:00 > 0:38:01or drinking water.
0:38:01 > 0:38:05Around 10,000 people were killed.
0:38:07 > 0:38:09It's very clear that the 1985 earthquake
0:38:09 > 0:38:11cast a long shadow.
0:38:11 > 0:38:13They don't want that to happen again, they're not going to let
0:38:13 > 0:38:15their fellow citizens suffer like that again,
0:38:15 > 0:38:18so they've got the tools, they've got the training,
0:38:18 > 0:38:20and they've got the techniques.
0:38:20 > 0:38:22I'm not sure I'd cut it on their team.
0:38:24 > 0:38:28Rescue teams are Mexico City's last line of defence.
0:38:29 > 0:38:31But that's not all.
0:38:31 > 0:38:35In a city where millions live in self-built houses,
0:38:35 > 0:38:36they've also developed
0:38:36 > 0:38:40the most effective early warning system in the world.
0:38:40 > 0:38:43It buys people crucial time to evacuate.
0:38:45 > 0:38:48I've come to the National Seismological Service
0:38:48 > 0:38:52at Unam, the National Autonomous University of Mexico,
0:38:52 > 0:38:55to meet Dr Xyoli Perez-Campos.
0:38:55 > 0:38:57How far down are we going?
0:38:57 > 0:38:59We are going to go 20 metres down.
0:38:59 > 0:39:0120 metres, OK.
0:39:02 > 0:39:06At the bottom of this shaft are highly advanced seismic sensors.
0:39:07 > 0:39:10These are the latest technology
0:39:10 > 0:39:14and the most precise instrument in the world.
0:39:14 > 0:39:18They're part of a network of more than 150 sensors
0:39:18 > 0:39:21constantly monitoring the Earth for tremors.
0:39:21 > 0:39:24Did this detect Haiti? Did it detect Pakistan?
0:39:24 > 0:39:26Yes. Like Japan, 2011.
0:39:26 > 0:39:27Isn't that amazing?
0:39:27 > 0:39:30That something that's happening on the other side of the planet
0:39:30 > 0:39:32can be detected here in Mexico City.
0:39:34 > 0:39:35The tremors picked up by the sensors
0:39:35 > 0:39:38are monitored right here at the University.
0:39:38 > 0:39:43We report daily an average of 32 earthquakes per day.
0:39:43 > 0:39:48Hang on a minute - 32 earthquakes every day on average?
0:39:48 > 0:39:50- Yes, yes.- That's a huge figure.
0:39:52 > 0:39:56Most earthquakes are small tremors that few people notice.
0:39:56 > 0:40:00But when a bigger quake strikes, the early warning system kicks in.
0:40:03 > 0:40:06With the main fault line 200 miles away,
0:40:06 > 0:40:09this technology gives more than a minute's warning
0:40:09 > 0:40:11before the shock waves actually hit.
0:40:14 > 0:40:17It's a system that saves lives.
0:40:17 > 0:40:18So you'll have detected one today?
0:40:18 > 0:40:23Yes - actually, this morning, we have a big one.
0:40:23 > 0:40:28It had a magnitude of 5.6 and we can see the record on the screens.
0:40:28 > 0:40:31It happens off the coast of the country,
0:40:31 > 0:40:34so it was in the Pacific, so nobody felt it.
0:40:34 > 0:40:36When do you think the next earthquake will hit here?
0:40:36 > 0:40:39Well, today, we will have one, but a small one, of course.
0:40:39 > 0:40:41We don't know if a big one is going to happen
0:40:41 > 0:40:43or when it's going to happen.
0:40:49 > 0:40:51The more we explore this city,
0:40:51 > 0:40:55the more we're learning it works because it doesn't live in fear.
0:40:57 > 0:41:00Its streets positively brim with life.
0:41:00 > 0:41:04That optimism underpins big plans for the future.
0:41:05 > 0:41:07The sprawl can't go on forever...
0:41:08 > 0:41:10..so there's only one way to build,
0:41:10 > 0:41:12and that's up.
0:41:14 > 0:41:16But how do you build a skyscraper
0:41:16 > 0:41:20on an unstable lakebed in an earthquake zone?
0:41:22 > 0:41:24This is the Torre Reforma.
0:41:26 > 0:41:30Standing 256 metres and 57 storeys high,
0:41:30 > 0:41:32it's Mexico City's tallest building.
0:41:34 > 0:41:36- Hello.- Welcome.
0:41:36 > 0:41:38- VOICEOVER:- Its architect, Benjamin Romano,
0:41:38 > 0:41:40is here to show me the secrets
0:41:40 > 0:41:42behind this incredible feat of engineering.
0:41:44 > 0:41:46Embedded in the concrete slab,
0:41:46 > 0:41:51we have this connection that goes to the edges of the concrete wall,
0:41:51 > 0:41:54so in the case of an earthquake,
0:41:54 > 0:41:58these elements will control the building not to move
0:41:58 > 0:42:02where the building doesn't want to move.
0:42:02 > 0:42:08- So it lets it flex a bit, but not too far.- Exactly.
0:42:10 > 0:42:13In sinking the foundations of the skyscraper,
0:42:13 > 0:42:16Benjamin needed to take into account the city's waterlogged past.
0:42:18 > 0:42:23Those concrete walls are embedded 60 metres underneath the street.
0:42:23 > 0:42:27- So you've gone below the lakebed, all the way down?- Exactly.
0:42:27 > 0:42:31So for us, the earthquake issue because of the lake means nothing.
0:42:31 > 0:42:33Now that I've seen this, I'm feeling more confident
0:42:33 > 0:42:36about going up Mexico City's tallest building.
0:42:36 > 0:42:38I think, even if there's an earthquake, we're going to be fine.
0:42:38 > 0:42:40- You are going to be perfectly safe. - OK.
0:42:43 > 0:42:47There are 28 lifts serving more than 4,000 people.
0:42:47 > 0:42:50Everything in this cutting-edge building
0:42:50 > 0:42:55is designed not only for looks, but also for safety.
0:42:55 > 0:42:59So, Benjamin, these windows are a very unusual shape.
0:42:59 > 0:43:03Yes. Since they have to behave in case of an earthquake,
0:43:03 > 0:43:07these window needs to move 10cm.
0:43:07 > 0:43:09The windows in this building
0:43:09 > 0:43:11are designed to bend and flex during an earthquake
0:43:11 > 0:43:13to release the build-up of pressure.
0:43:15 > 0:43:18So this is like leaving a ready-made crack in the side of a building?
0:43:18 > 0:43:23Yes, exactly. It's to allow the two different elements to move.
0:43:23 > 0:43:27It's so strange talking about high-rise buildings moving,
0:43:27 > 0:43:31because from the ground, they look so static and strong,
0:43:31 > 0:43:34and here you are, telling me that they're always in movement.
0:43:34 > 0:43:38They all have to move, because either for wind or seismic...
0:43:38 > 0:43:40It's like if I push you -
0:43:40 > 0:43:43they will move and come back to the natural.
0:43:46 > 0:43:50This iconic building, now punctuating the skyline,
0:43:50 > 0:43:52looks to the future of Mexico City.
0:43:52 > 0:43:54It's earthquake resistant,
0:43:54 > 0:43:58it has its own rain and waste water harvesting system,
0:43:58 > 0:44:02and it even has robots that will park your car for you.
0:44:02 > 0:44:06- VOICEOVER:- On top of all that, it has quite a view.
0:44:10 > 0:44:13I mean, I'm almost speechless at how big Mexico City is.
0:44:13 > 0:44:15I mean, from up here, it just stretches...
0:44:15 > 0:44:18- Well, it stretches as far as the eye can see.- Yes.
0:44:18 > 0:44:20Did you ever think you'd be responsible
0:44:20 > 0:44:21for the tallest building in Mexico?
0:44:21 > 0:44:22Never in my life.
0:44:22 > 0:44:28It is a very unique feeling. So far, I'm very happy.
0:44:30 > 0:44:33Standing here on top of the tallest building in Mexico City,
0:44:33 > 0:44:36I'm in awe of what Benjamin and his team have achieved.
0:44:36 > 0:44:39Their ingenuity has overcome so many hurdles
0:44:39 > 0:44:40placed in their way by nature,
0:44:40 > 0:44:44and if Mexico City represents a battle
0:44:44 > 0:44:47between human habitation and nature,
0:44:47 > 0:44:49this is a war-winning strategy.
0:44:54 > 0:44:58Building for the future here doesn't stop at skyscrapers.
0:44:59 > 0:45:04Getting 22 million people in and out of the crowded city every day
0:45:04 > 0:45:08is a challenge, especially with its haphazard bus service.
0:45:11 > 0:45:13But I've come to the suburb of Ecatepec
0:45:13 > 0:45:16to discover that almost anything can be built
0:45:16 > 0:45:18in this spirited city.
0:45:19 > 0:45:21Well, wow, look at this -
0:45:21 > 0:45:23it's just like everything else here in Mexico City,
0:45:23 > 0:45:25a big surprise.
0:45:25 > 0:45:28The last thing I was expecting to find here is a cable car.
0:45:30 > 0:45:31It's accessible as well.
0:45:31 > 0:45:34There's a wheelchair entrance, there's a ramp -
0:45:34 > 0:45:36I'm loving it already.
0:45:51 > 0:45:53The views from the Mexicable,
0:45:53 > 0:45:57you've got this sprawling city and these murals
0:45:57 > 0:46:00and the amazing colours on the houses.
0:46:00 > 0:46:02It's just breathtaking.
0:46:08 > 0:46:12This cable car system was only completed in 2016.
0:46:12 > 0:46:17It costs just six pesos, or 26p, to ride,
0:46:17 > 0:46:21and already, nearly 30,000 people are using it every day.
0:46:24 > 0:46:27- VOICEOVER:- Victor Jasso is the engineer
0:46:27 > 0:46:29who keeps the system running smoothly.
0:46:29 > 0:46:33So, Victor, why build it here and why build it now?
0:46:33 > 0:46:36Because this area has a really big problem.
0:46:36 > 0:46:41There's not too much roads, there are not so much highways,
0:46:41 > 0:46:44so we have a lot of people living here,
0:46:44 > 0:46:47so a cable car, it's totally a solution.
0:46:47 > 0:46:51You don't have a stoplight, you don't have traffic.
0:46:51 > 0:46:53So now they're more connected...
0:46:53 > 0:46:56Yes, yes, that's the word, connected.
0:46:56 > 0:47:00Can you tell me about the mechanics? What goes into this?
0:47:00 > 0:47:04Cos it looks like an enormous engineering feat.
0:47:04 > 0:47:07This cable car is moved by an engine.
0:47:07 > 0:47:10The engine is the big red one over the station,
0:47:10 > 0:47:13and with that engine, we move the whole loop
0:47:13 > 0:47:15between station four to station one.
0:47:15 > 0:47:19The one engine moves all of these cars across four stations?
0:47:19 > 0:47:21- Yes.- Wow.
0:47:23 > 0:47:26There are seven cable car stations in total,
0:47:26 > 0:47:28running just over three miles,
0:47:28 > 0:47:30connecting some of the city's poorest
0:47:30 > 0:47:32and most isolated hillside neighbourhoods.
0:47:34 > 0:47:38The system is run from control rooms like this.
0:47:38 > 0:47:41With this button, we can reduce the speed,
0:47:41 > 0:47:43because sometimes, we have some people
0:47:43 > 0:47:47that maybe need more assistance.
0:47:47 > 0:47:49Actually, we've got a wheelchair customer,
0:47:49 > 0:47:50do you need to slow it down?
0:47:50 > 0:47:53Yeah. Just put it in lento uno.
0:47:53 > 0:47:56- Speed...- The speed reduces... - So it makes it slower?
0:47:56 > 0:48:00- Yeah.- And this now allows this lady in a wheelchair to get in easier?
0:48:00 > 0:48:01Yes.
0:48:03 > 0:48:06- VOICEOVER:- This technology is really unexpected.
0:48:06 > 0:48:08It looks like it's quite easy for him to pull.
0:48:08 > 0:48:10Yeah, and it's really, really easy for pushing.
0:48:10 > 0:48:14You know, it's amazing, the cabin, it's one tonne.
0:48:14 > 0:48:16So this is a tonne and we can just push it?
0:48:16 > 0:48:19- Yeah.- Wow, that is so easy!
0:48:19 > 0:48:22Look at that, one finger. Look at that!
0:48:24 > 0:48:25That's incredible.
0:48:26 > 0:48:28That system is so smooth.
0:48:28 > 0:48:32I need that for my wheels on my chair.
0:48:33 > 0:48:37This all makes for a very different commute for local residents.
0:48:38 > 0:48:41- Hola.- Hola, buenos dias. - Buenos dias.- Como estas?
0:48:41 > 0:48:43- VOICEOVER:- Daniel Gimelo is a shoe shiner.
0:48:43 > 0:48:46Every day, he travels on the cable car with his bike,
0:48:46 > 0:48:50then cycles the rest of the way into the centre to find work.
0:49:21 > 0:49:24It's morning rush hour and commuters like Daniel
0:49:24 > 0:49:27are flooding onto the cable car to get to work.
0:49:27 > 0:49:29But it doesn't just save them time.
0:49:29 > 0:49:34Juan Martinez Jurado uses the cable car every day.
0:50:24 > 0:50:26This new public transport system
0:50:26 > 0:50:28hasn't just improved the commute for locals -
0:50:28 > 0:50:32it's also transformed the surrounding neighbourhood.
0:50:32 > 0:50:35It's incredible, it's almost like this Mexicable
0:50:35 > 0:50:37has given this whole area a face-lift.
0:50:38 > 0:50:42All of these images and paintings have just sprung up
0:50:42 > 0:50:44because of the Mexicable.
0:50:44 > 0:50:47And what it's done is it's just lifted the ambiance
0:50:47 > 0:50:49of this whole area.
0:50:49 > 0:50:50It's just made it really beautiful,
0:50:50 > 0:50:53and it's such a nice way to get to work, I think.
0:51:01 > 0:51:04There's a feeling all across Mexico City
0:51:04 > 0:51:05that it's cleaning up its act.
0:51:08 > 0:51:10And not a moment too soon,
0:51:10 > 0:51:14because Mexico and its capital have a poor reputation for crime.
0:51:16 > 0:51:18To find out how this city polices
0:51:18 > 0:51:22a sprawl of almost 1,000 square miles,
0:51:22 > 0:51:23I'm taking to the air.
0:51:27 > 0:51:30Well, we're just about to take off, now, the aircraft is warming up.
0:51:30 > 0:51:34We are going in the Mexico City police observation helicopter.
0:51:34 > 0:51:37This is the key to making sure that a relatively small police force
0:51:37 > 0:51:40is able to maintain law and order in this vast and complicated city.
0:51:40 > 0:51:45It's using the eye in the sky, linked to the ground technology.
0:51:50 > 0:51:55In Mexico City, there are almost 90,000 police officers.
0:51:55 > 0:51:58Officer Carlos Moreno is a specialist camera operator
0:51:58 > 0:52:02who works the skies in one of 13 helicopters.
0:52:02 > 0:52:08How hard is it to keep order in a city of over 20 million people?
0:52:08 > 0:52:09So difficult.
0:52:09 > 0:52:11As you see, it's really big.
0:52:11 > 0:52:16But we have excellent communication with ground units.
0:52:16 > 0:52:18We got, also, all the time,
0:52:18 > 0:52:20one helicopter flying around the city.
0:52:20 > 0:52:23We can cross the city in five minutes.
0:52:25 > 0:52:29With this technology, Carlos can home in on one target
0:52:29 > 0:52:31in a city of millions.
0:52:31 > 0:52:34I'm going to show you how we follow a car.
0:52:34 > 0:52:37We can follow automatically.
0:52:37 > 0:52:39I don't have to move anything.
0:52:39 > 0:52:41That's clever, so you can track a target.
0:52:41 > 0:52:43Once you lock onto it, yeah.
0:52:43 > 0:52:45How much closer can you go?
0:52:45 > 0:52:46Could you read the license plate on there?
0:52:46 > 0:52:48We are going to try.
0:52:51 > 0:52:52That's astonishing.
0:52:52 > 0:52:55- Yeah.- You can see right into the back of his vehicle.
0:52:55 > 0:52:57Yeah, exactly.
0:52:57 > 0:52:59- VOICEOVER:- The police can track suspects
0:52:59 > 0:53:01all the way across this huge city.
0:53:02 > 0:53:05Down is down, up is up, left and right, it's the same.
0:53:05 > 0:53:07- And you zoom in like this? - And you're going to follow...
0:53:07 > 0:53:09That's incredible.
0:53:09 > 0:53:12I feel like I'm going to crash into that building!
0:53:16 > 0:53:20Air units like this allow the police to stay one step ahead.
0:53:24 > 0:53:30This is a sprawl that spreads as far as I can see in all directions.
0:53:30 > 0:53:33It would take hundreds of thousands of policemen and women on the ground
0:53:33 > 0:53:34to maintain control,
0:53:34 > 0:53:38but, by using this, you can use those other resources
0:53:38 > 0:53:40far more efficiently.
0:53:40 > 0:53:43Technology like this is an essential ingredient
0:53:43 > 0:53:46if these modern megacities are to be sustainable and safe.
0:53:51 > 0:53:53While Dan avoids the traffic in the sky,
0:53:53 > 0:53:56I'm in the thick of it on the ground.
0:54:00 > 0:54:04Monday morning rush-hour traffic in Mexico City,
0:54:04 > 0:54:06but it's not as bad as it normally is,
0:54:06 > 0:54:10because the smog levels have been so high this week.
0:54:10 > 0:54:15In fact, the highest smog levels recorded in the last 20 years.
0:54:15 > 0:54:17HORN BLARES It's all happening here.
0:54:17 > 0:54:18Get it into gear, mate.
0:54:20 > 0:54:21And off he goes.
0:54:21 > 0:54:25The smog levels are so high that the authorities take measures
0:54:25 > 0:54:27to reduce the number of cars on the road,
0:54:27 > 0:54:29so even though this looks insane,
0:54:29 > 0:54:31it's not half as bad as it normally is.
0:54:38 > 0:54:41But something is changing here.
0:54:41 > 0:54:43Take a walk around the streets nearby
0:54:43 > 0:54:46and the atmosphere becomes noticeably calmer.
0:54:48 > 0:54:49Pimped.
0:54:52 > 0:54:55This is Paseo de la Reforma,
0:54:55 > 0:55:00a wide avenue running diagonally across the heart of Mexico City.
0:55:00 > 0:55:03It's usually full of cars, but not today.
0:55:03 > 0:55:06- Hola, Areli.- Hola. - Lovely to meet you.
0:55:06 > 0:55:10VOICEOVER: Areli Carreon is a cycling enthusiast and campaigner.
0:55:10 > 0:55:13She's also Mexico City's first-ever bike mayor.
0:55:13 > 0:55:16I'm totally blown away by what's happening.
0:55:16 > 0:55:19- Tell me, it's a Sunday morning. - Yes.- What is this?
0:55:19 > 0:55:20Is this a one-off event?
0:55:20 > 0:55:22No, it happens every Sunday,
0:55:22 > 0:55:26and it's a close-down of a main street in Mexico City.
0:55:26 > 0:55:29This is Reforma, one of the most historical
0:55:29 > 0:55:32and most iconic streets in the city.
0:55:32 > 0:55:35- This is like shutting down the Champs-Elysees.- Yes.
0:55:35 > 0:55:37There's, like, 50,000 people
0:55:37 > 0:55:41and, as you can see, there's people from all walks of life here
0:55:41 > 0:55:42enjoying the city.
0:55:42 > 0:55:45- Somebody's listening to their music whilst they're cycling.- Yeah.
0:55:45 > 0:55:49Oh, it's not just a little bit, he's got a massive ghetto blaster.
0:55:49 > 0:55:51Yeah. Look at that.
0:55:53 > 0:55:55All of this cycling is yet another way
0:55:55 > 0:55:59this massive megacity is cleaning up its act.
0:55:59 > 0:56:01Mexico City has, like most major cities,
0:56:01 > 0:56:03a real problem with pollution, doesn't it?
0:56:03 > 0:56:06Yeah, of course. The average speed in the city on a car
0:56:06 > 0:56:10is the same as bicycling, it's 15kmph, which is insane.
0:56:10 > 0:56:13If we don't do something about this,
0:56:13 > 0:56:16eventually, we wouldn't have enough clean air to breathe.
0:56:19 > 0:56:22This city loves to live life on its streets.
0:56:22 > 0:56:25That's amazing, look - he's got Grandma on the front,
0:56:25 > 0:56:27baby on the back, maybe that's his grandson.
0:56:27 > 0:56:29One of the things that I like the best
0:56:29 > 0:56:33is it doesn't matter who you are, which is your walk of life,
0:56:33 > 0:56:36people get to be together and enjoy
0:56:36 > 0:56:39and have a conversation and just be around.
0:56:42 > 0:56:44Well, I feel like you're telling me to get on this bike.
0:56:44 > 0:56:46I feel like, subliminally, you're just like,
0:56:46 > 0:56:49- "Anita, I've got you a bike." - Let's go!- "Get on."
0:56:49 > 0:56:52- Shall we?- Yes.- I feel like we should join everybody.
0:56:52 > 0:56:54Let's go.
0:56:54 > 0:56:55Whee-hee!
0:57:00 > 0:57:01Oh, it's great fun.
0:57:03 > 0:57:05It's such a brilliant way to see the city as well.
0:57:12 > 0:57:15What a great bit of progressive civic planning,
0:57:15 > 0:57:17cos at the heart of every city are its people,
0:57:17 > 0:57:19so let the people take over the streets.
0:57:19 > 0:57:21On top of that, it's great fun.
0:57:21 > 0:57:23BELL RINGS
0:57:27 > 0:57:31Mexico City is full of surprises.
0:57:32 > 0:57:35This is a city where cars are giving way to bicycles...
0:57:37 > 0:57:39..where cutting-edge cable cars
0:57:39 > 0:57:41glide over self-built neighbourhoods...
0:57:43 > 0:57:45..where sprawl meets skyscrapers.
0:57:47 > 0:57:50It may be fighting a daily battle with Nature,
0:57:50 > 0:57:54but it's a fight that its enterprising, optimistic
0:57:54 > 0:57:57and resilient citizens are determined to win.
0:58:01 > 0:58:04Next time...we're in Moscow...
0:58:04 > 0:58:05Muscovites everywhere.
0:58:05 > 0:58:10..exploring a city forged by power and politics,
0:58:10 > 0:58:12that plays by its own rules.
0:58:14 > 0:58:19I've never been allowed inside the red walls of the Kremlin before.
0:58:19 > 0:58:22Uncovering the systems and traditions...
0:58:22 > 0:58:23Are you on time?
0:58:23 > 0:58:26Honestly, I'm three hours late.
0:58:26 > 0:58:30..that make this one of the world's busiest cities.