SÃO PAULO — In "Cracolandia" (Crackland), in the Brazilian megalopolis of São Paulo, almost anything can be exchanged for drugs: a shower head, an empty rucksack, cachaça, headphones, radio-controlled cars, a lampshade. One boy walks around carrying a chair. He's hoping to barter it for crack. He stops outside a shack. A trafficker looks at him and makes a gesture indicating "no deal." A chair isn't worth a rock around here. A guy with a pair of sneakers has better luck. "Who wants a pair of Nikes? I've got a pair of Nikes," he shouts. Moments later he makes an exchange.

After a major police operation at the end of May, drug traffickers and users moved from the streets they used to occupy in central São Paulo to this area in Princess Isabel square. It's about 400 meters from the previous Crackland, which São Paulo's mayor, João Doria, described as an "open-air shopping mall for drugs." The new Crackland is already growing unremittingly, with an almost exclusively male population that can reach up to 1,000 people, depending on the time of day. And so on June 11, police again intervened.

The tarpaulin tents that make up Crackland have two main functions: they protect against the cold and the rain and they provide shelter for drug trafficking. Inside the tents are small tables on which all sorts of products are kept: crack rocks, drinks, lighters, cigarettes, pipes. The traffickers remain behind these tables as they negotiate sales or barters, but they don't deal to all drug users. There's also a more subtle way of trafficking, where drug users themselves pass rocks to one another.

The "flow" of selling, bartering and consuming is less intense during the day, in part because of the presence of dozens of social and health workers trying to convince addicts to seek treatment. Most of the time, the police presence is limited to two military police vehicles with four officers in each. But access to the square isn't restricted, and the trafficking takes place without intervention.

At nightfall, the flow expands. Hundreds of people appear, looking for drugs and drinks. At night in Crackland, there are two types of people. First, the homeless, who make up about 80% of the population in Crackland. The vast majority are either unemployed or work in undeclared small jobs. The other group is fluctuating, and includes clean, well-dressed people, many in their 20s and 30s but some over 45. One man enters the area, wearing suspenders and a hat. These people never stay too long. They buy their drugs (crack, cocaine, marijuana), they smoke it, they leave.

Rogério, 37, says he comes "once or twice a week" to smoke crack. "I come here, I buy my drugs, I take them and I go and sleep," he says. "I don't stay here all day."

Dancing til dawn

It's 2:30 a.m. and Crackland is still wide awake. Portable loudspeakers spit out funk and rap beats. The sound of hammers pounding on tent pegs mixes with the noise of the shopping carts the homeless walk around with. It doesn't stop. One man plays a ukulele. Another starts playing a guitar solo that soon dies out.

Little by little, the area turns into a sort of rave, with people taking drugs, drinking and dancing until the crack of dawn. People light fires to keep warm, and the smoke adds another layer to the smell of feces. A young man climbs on one of the square's playground structures — a jungle gym — and in under 10 minutes builds a home for himself on the top part. The playground becomes an estate. The tunnel under a slide turns into a shelter for more drug-taking.

Day and night, young boys ride their bikes in and out of Crackland. There are also people walking around barefoot, others lying on the ground, which becomes muddy when it rains. Others pick through the trash, looking for something to eat or for iron to make a pipe.

Compared to its previous version, where drug users stayed one street and traffickers on another, the new Crackland is more of a maze. It also has a "bar," which is actually a 10-meter long tent. Beyond crack pipes, the bar also sells White Horse whiskey, brandy, beer, catuaba (an aphrodisiac infusion), cigarettes, lighters, water and other soft drinks. Workers take turns. One young man works there until 10 p.m. before being replaced by a blond woman who spends part of the night looking at her phone. Every now and then, a man comes to refill the stock with new products.

There is also food available in Crackland, though at least one in every five people we talked to hadn't eaten at all over the previous 24 hours. Not far from the bar, one man sells sandwiches. He's got bread, a bag of olives, parsley, lemon, meat, mustard, pepper, margarine, tomato sauce and salt. To fry the meat, he makes a fire inside a shopping cart and puts his frying pan on top. Other tents specialize in making pipes. The owners of those "shops' spend their night preparing food that they then exchange for rocks, or anything deemed good enough to accept.

Of course, this all takes place in a cloud of crack smoke. Anybody who comes just to eat a sandwich also gets his share of second-hand crack fumes — even the man selling the sandwiches smokes.

Children and teenagers also roam freely in Crackland. One of the dealers is actually a boy, aged about 12. He stands in front of a table, together with a woman. Both are partly hidden behind an umbrella. In the early hours of the night, a big, shirtless man — not exactly the sort you imagine taking drugs — comes looking to buy some crack. The child prepares the man's fix. Another boy, Danilo, 13, admits he comes to take drugs. "But I don't live here," he says looking at his feet.

The atmosphere is generally friendly. We didn't see any fights, just some people arguing, but nothing serious. We did, however, witness three police officers beating up a young man. Others rebelled and tried to intervene. In a matter of minutes, six cars from the municipal guards came and the crowd dispersed.

After the first police operation, Mayor Doria proclaimed the end of Crackland. Since then, though, little has changed for the drug users. But people are a bit more wary, not sure who to trust. Anybody, they worry, could be a police officer working undercover... or a journalist.