Located on a steep hillside, just a half-mile from some of the world’s most beautiful beaches, Rocinha (pronounced “ha-see-nyah”) is Rio de Janeiro’s biggest favela, or shantytown, and the largest — and most developed — shantytown, in fact, in all of South America. A symbol of Brazil’s economic disparities, in the favela, drugs, gangs, poverty, unemployment and school dropout are rampant. This page and opposite, counterclockwise from above: In Rocinha, members of A.D.A., or Amigos dos Amigos (“Friends of Friends” in English), the favela’s ruling drug gang, patrol an alley to prevent rival gangs and police from entering the community; teenaged Rocinha residents smoke pot on a rooftop; a motorbike taxi with a young female passenger passes a burned-out car in Rocinha; on Rio’s Copacabana beach, with its famous swirl-pattern mosaics, the rich and upper-middle class enjoy the surf and sun, while the nearby favelas are separated from the beaches by mountains. East Village photographer Q. Sakamaki took these photos during May and June of this year. Sakamaki also shot the funerals of two police officers — one killed in a carjacking, the other in gunfight with a drug gang — inmates of a prison for minors and the bodies of a mother and her three children slain in domestic violence. Although Sakamaki was not bothered by A.D.A., members of another gang stole two of his cameras: They asked him in Portuguese what time it was, and when he looked up from his wristwatch they were holding guns on him.