Built in the 1960s, Cidade de Deus (City of God) is a sprawling housing project built to keep the poor as far as possible from Rio's glamorous beaches and resorts. By the 1980s, it has degenerated into a war zone so dangerous that visitors from outside risk being shot to death on sight, a poisonous stew of poverty, drugs, and crime. "If you run away, they get you, and if you stay, they get you, too," says Rocket, who wants to be a photographer. Rocket's...