Behind the finer points of any counter-bandido strategy is of course the question of whether the government can start providing basic services to hundreds of thousands of its poor. Rocinha strikes me, during my handful of visits, as in many ways a very happy place. Fernando certainly likes his life there very much. Even when I ask Natalia if she likes living in war-torn Maré she replies, "I like it. I love it — the way people help each other, support each other, and act as an integrated community. And the love." Natalia's single mother is in jail, and it is proof of this communal love and support that she and her six younger siblings are surviving from day to day. She is taking general studies classes at Luta Pela Paz, and dreams of going to university to study medicine — "But even as a surgeon, I will live here." However, there are other favelas in Rio where it would be impossible to ask people if they liked their life.

Pierre Yves, a Frenchman who settled in Rio 20 years ago and volunteers for an awareness-raising group called Rio de Paz ("River of Peace"), takes me to Mandela de Pedra, a favela of about 2,500 people that is part of the Complexo de Manguinhos (60,000 people). We enter Mandela de Pedra on foot, by a road off a dusty highway in Rio's North Zone. The turn-off is marked by graffiti that reads, in large letters, "CV. Who betrays, pays!!!!" The road runs along a blighted river, and the Commando Vermelho have erected a tall barrier to shield it from view from the opposite bank. On 28 October 2009, Rafael Rocha Ribeiro, a 15-year-old with no connection to the drugs trade, was killed here by policemen taking pot-shots from the far side. At the end of this long channel, two bandidos with holstered pistols sit at a desk, a kind of reception, watching who approaches and presumably selling drugs to anyone mad enough to come here for them. The favela is full of children, toddlers standing in dark doorways in their underwear, older kids clambering about on mountains of garbage. They're very excited to see a pair of gringos, and they follow us around, asking us to speak in our strange languages. One boy asks Pierre whether he, too, eats — "as if I am E.T." Deep puddles of contaminated water are everywhere. Even here the adults greet us with "Good day" and the ubiquitous Brazilian greeting, "All well?" In one home we're introduced to a severely disabled young girl who smiles prettily up at us as she spasms inadvertently on the floor. Pierre is the quintessential charity worker. He looks harrowed, totally shot, but he floats around inquiring after small details, friendly and pragmatic, seeing what little things can be done.

Later Pierre takes me to a prison, or to be precise, a polinter in Neves, on the East side of the Guanabara Bay. It isn't a state facility, but a local holding prison for men on remand. "I'm convinced," he tells me on the way there, "that the cycle of crime cannot be broken with the conditions of detention you are about to see. It is just made worse. The conditions are like the inside of a slave ship. And here, I will introduce you to a member of the Commando Vermelho."

The polinter is divided into two wings, each consisting of a corridor that joins four cells of about 15 by 30 feet in size. The Commando Vermelho, and other men who just happen to live in their territories, are in one wing. Everyone else is in the other. Each cell has 16 bunks, but each wing contains about 300 men, and it's about 60 or 70 to a cell, with hammocks hung to make up the bed-space. I follow Pierre around as he goes from cell to cell, talking with prisoners.

When Rio de Paz first came here six months ago, the cell doors were locked. Now, the prisoners can at least move from cell to cell within their wing and mill about, shoulder-to-shoulder in the corridor. But the truly savage thing about this place is that at no time can they go outdoors. The only windows are high on the walls of the corridor, and even through them the sky is concealed by the eaves of the building.