EUGENIE BIRCH: Imagine building a city for a million people every week for the next 40 years.Imagine what that would take.



NARRATION: Medelln, Colombia. Colombia isnt the largest country in South America, and Medelln isnt even the largest city in Colombia. But theres something happening here thats made it a window into the future of cities

ANGELA PUELLO (TRANSLATED FROM SPANISH): Its a place where one can hang out. Its very safe.

WILSON MEJA (TRANSLATED FROM SPANISH): Its a is paradise, not because it is my neighborhood, but it is a paradise.

NARRATION: Wilson Meja and Angela Puello arent just small business owners, theyre participants in an unusual urban experiment. One thats happening in a place whose past might never lead you to believe itd be a model for the future.

ARCHIVAL (ABC NEWS, 9-4-89):PETER JENNINGS: The city with the highest murder rate in the world

NARRATION: If you know anything about Colombias second largest city, its probably that, in the 80s and early 90s, Medelln was headquarters for a homicidal drug cartel headed by Pablo Escobar, and the bombings and bloodshed from the drug trade regularly spilled into the streets.

ARCHIVAL (NBC, 7-15-90):ANCHOR: In Colombia, the murders continue in the cocaine capital of Medelln. Forty deaths have been reported there in the last 24 hours.

NARRATION: Some of the worst violence plagued Medellns slums. For decades, these makeshift neighborhoods were hacked out of outlying hillsides by migrants who were too poor to find homes in the city center. Perhaps the most notorious of these was Santo Domingo, where Wilson Meja lived when he was a kid.

WILSON MEJA (TRANSLATED FROM SPANISH): There was no law.I saw a lot of violence, they were already killing a lot of people, 2 or 3 killed every day. Chases, gunfire.

NARRATION: Wilsons family first arrived when he was 3 years old, joining one of many waves of rural migrants who flocked to Medelln. Some were pushed from the countryside by Colombias decades-long civil war, others were pulled by the promise of better jobs. But the only place they could live were the illegal shantytowns beyond the reach of police or city services.

WILSON MEJA (TRANSLATED FROM SPANISH): We did not have water that arrived directly through the pipeline. I had to go find it in nearby neighborhoods where there was a spring. It was impossible to get up here.

NARRATION: And yet, the city continued to be overwhelmed with newcomers. In just five decades, Medellns population exploded from 300,000 people to nearly 3 million. And Medellns story is in many ways the whole worlds story. Our planet moving to town, and faster all the time. It took more than 10,000 years from the dawn of human settlement to 1800 for the human population to become just under 3 percent urban. By 1950, we were 30 percent urban. And by 2050, some projections say 70 percent of humanity will end up living in cities.

EDSIO FERNANDES (AUTHOR, REGULARIZATION OF INFORMAL SETTLEMENTS IN LATIN AMERICA): So if there is a legacy for the future generations, it is the fact that theyll be living in cities.So what citieswhat kind of cities?

NARRATION: And many of the new arrivals will end up making their living the informal, hand-built shantytowns that are sprouting in cities across the developing world.

EDSIO FERNANDES: Often you are talking about 50 percent, 60 percent, of the people living informally. So we are not talking about the exception, right? So the city is that.

JANICE PERLMAN (AUTHOR, FAVELA): The population living in the slums in the large cities in the Global South represent at this very moment a billion people.

NARRATION: Wilsons family eventually left Medelln as the city became more violent, but many more migrants kept coming. And many of them arrived during an economic downturn when Medellns factories were in decline, and the drug trade was on the rise.

JULIO DVILA: The city was at the point of collapse. It was that serious.

OMAR URN (PROFESSOR, UNIVERSITY OF ANTIOQUIA, TRANSLATED FROM SPANISH): There was a lot of fear. I mean, the city was falling apart.

NARRATION: But contrary to the expectations of many observers, the crisis in Medelln forced a change. Voters fed up with the violence elected a series of reformist mayors, who joined with activists, urban planners and business owners to invest heavily in upgrading some of poorest informal neighborhoods to connect them with the rest of the city.

JUSTIN MCGUIRK (AUTHOR, RADICAL CITIES): The key policies bridged this psychological divide between the City Center and the very poor comunas on the hillsides, which were fairly detached from the city.

NARRATION: One of most innovative of these policies bridged this gap literally. Medelln had built an above-ground metro system to help people get around the middle of town, down on the valley floor. And nine years later, they added these.

JUSTIN MCGUIRK: Building a cable car from the City Center to the poorest neighborhood, Santa Domingo, in the hills, was hugely significant in crossing this psychological barrier.

NARRATION: Its among the first in the world to be used for urban mass transit, and it was part of a multi-billion dollar campaign to knit the property and the people of informal neighborhoods into the formal city. At times, as much as a quarter of the Medellns budget came from a publicly-owned power utility, which drew money from all over the region to upgrade city slums.

JULIO DVILA (PROFESSOR, UNIVERSITY COLLEGE LONDON): In addition to the cable car, there were other crucial investments that provided additional opportunities to peopleschools for the kids, libraries, microcredit. If we were to look at the costs, there were probably eight times as big as the cost of building the first cable car.

NARRATION: Thirteen years ago the recovery convinced Wilson to move back to Medelln. Just down the hill from the new Metrocable station, he and Angela opened two bars and a restaurant on the same street.

WILSON MEJA (TRANSLATED FROM SPANISH): Once the Metrocable project started, the city administration started opening offices here, like the house of justice, inspections, lot of entities. So, here we dont pay tribute to gangs, we are ruled by the town hall.

NARRATION: Angelas younger sister, Karen, she helps out at the restaurant. And she rides the cable car every time she commutes to nursing school.

KAREN PUELLO (TRANSLATED FROM SPANISH): My thoughts about living in Medelln changed after I decided to live here to study. For me today, Medelln represents a place full of opportunity.

NARRATION: Today, urban researchers from around the world have studied how Medelln upgraded and connected its shantytowns to the formal city. The lessons are easy enough to understand. But they may not be as easy replicate.

EUGENIE BIRCH: It boils down to politics basically and the political will to create cities without slums that accommodate low income people, that accommodate growth. Cities are where the economic activity of a nation occurs if the cities are well-functioning and well-run.

NARRATION: Perhaps the most fundamental change is how Medelln has accepted that informal settlements, and the people who live there, arent marginal to the citys success theyre essential to it.

EDSIO FERNANDES: Over time, and this is a basic principle of law.Over time, people get rights.

WILSON MEJA (TRANSLATED FROM SPANISH): Before a lot of people were ashamed to say they were from Santo Domingo. Now they live it with pride.

NARRATION: The changes have allowed the Meja family to find their own ways make the neighborhood a little better. They employ a couple of people. They offer food deliveries to busy neighbors. And for folks looking to relax, theres now a spot close to the metro station where you can grab a drink with friends, hear live music or watch the game.

WILSON MEJA (TRANSLATED FROM SPANISH): Of course it is the best bar in Santo Domingo. Its become a meeting place for the neighborhood.

EUGENIE BIRCH: Its not rocket science. We know what to do. We have the knowledge about how you lay pipes. We know how to set up transportation systems.But can you get places to do it? Thats the question.

NARRATION: Even here, success remains fragile. Workers may be laying foundations for new Metrocable lines in Medellns more established neighborhoods, but just up the valley, new shantytowns are growing.

Residents of this one, called Nueva Jerusaln, face many of same challenges the Meja family did decades ago. They pay an armed gang for plots of illegally occupied land, homes are built by hand and a lot of freight comes in on foot.

JOHANA SUAZA (TRANSLATED FROM SPANISH): We took the risk to come here to improve our way of life, and all of that. Even though we have a lot of needs, we are not about to stay with our arms folded over our chests. In spite of everything, we are sowers. To push forward, that is Nueva Jerusaln.

JANICE PERLMAN: The old way of thinking about slums was that they were a problem, an intractable, horrible problem that had to be dealt with by eliminating them. But the reality is that theyre the solution, and if theyre given the opportunity to contribute, they will be the key to sustainable cities in the future.