• Credit: Peter Arkle

The 2009 Oscar winner for best picture, Slumdog Millionaire, may have introduced Hollywood to the ragpickers of Mumbai, but that city’s scrap-heap squalor is all too common everywhere else.

In 2003, the United Nations reported that almost 1 billion people—about one-sixth of humanity, and a third of all city dwellers—lived in the slums of Africa, Asia, and Latin America, and the number was projected to double by 2030. Planning can’t keep up, so people ad-lib housing, often illegally, in the space they can find on urban fringes. A 2007 Economist report on Dharavi, a Mumbai slum, estimated that “a million residents [are] crammed into a square mile of low-rise wood, concrete and rusted iron”; from discarded bits, they cobble together lean-tos and shanties to fashion a community of their own—DIY cities.

The fastest-growing human habitat today, squatter villages—or favelas, as they’re called in Brazil—house a third of São Paulo and a fifth of Rio de Janeiro. In Shadow Cities (2004), journalist Robert Neuwirth insists that favelas are not a temporary phenomenon—they’re the future of urbanism: “Squatters mix more concrete than any developer. They lay more brick than any government. They have created a huge hidden economy. … [They] are the largest builders of housing in the world—and they are creating the cities of tomorrow.”

Pointing out that New York and London didn’t have paved roads, electricity, or sanitation systems until relatively recently, Neuwirth sees favelas as starter cities, the seeds of a future Paris or Barcelona. Already, they show many of the earmarks associated with sustainable development: compact footprints, high density, low energy use, little to no grading, reclaimed materials, humane scale, vibrant social interaction, and self-determination. Like Tuscan hill towns, their shapes and textures can be irresistible, as audiences of The Incredible Hulk (2008) discovered in the twisting alleys and terraced rooftops of Tavares Bastos, a Rio favela.

Will the city of the future be some hybrid of planned city and favela, combining the health, safety, and stable infrastructure of the former with the flexibility, resourcefulness, and communal creativity of the latter? As alternatives to planned cities, spontaneous settlements question customary views of community, property, urbanism, waste, value, and even beauty. Carving communities out of garbage dumps, these “slums of hope,” as the U.N. calls them, are monuments to human ingenuity and endurance.