"I decided to experience the real Jakarta," said a tourist, stepping gingerly between puddles of putrid water and a scurrying rat in a scene that would never make a postcard.
Rohaizad Abu Bakar, 28, a bank employee from Singapore, said he could not believe his eyes as he wandered around the slum - a jumble of hundreds of shacks beside a railway line in the Indonesian capital.
Nearby, a small girl picked up a discarded juice bottle in search of a sip and a man, wearing tattered shorts, lay slumped on a dirty old mattress. Only a blue plastic tarpaulin offered shelter from tropical downpours.
So-called "poverty tourism" is on the rise in Jakarta.
Organisers say it raises awareness and brings aid to the destitute of the city, but accusations of exploitation are never far away and critics say poverty should not be a tourist attraction.
A few hundred families cram into the slum in the Tanah Abang neighbourhood, minutes from gleaming shopping malls where the likes of Gucci and Louis Vuitton compete to lure the newly-minted beneficiaries of Indonesia's economic miracle.
Rather than seek out picturesque landscapes in other parts of the country, Abu Bakar opted to join a Jakarta Hidden Tours trip to see how the nation's poor live.
"Tourists stay in their ghetto. We show what is really Jakarta," says Ronny Poluan, 59, an Indonesian documentary-maker who created the non-profit organisation in 2008.
Recent years have seen "poverty tourism" mushroom around the world, from the favelas of Brazil to the slums of Dharavi in Mumbai, popularised by the film Slumdog Millionaire.
"We have about 10 tours per month, with two to four tourists each time," Poluan says.
"More and more people are coming, some now even come just for my tour.
"I've had tourists from as far away as Washington. They're not only backpackers, but also businessmen, bankers," he added before being cut short by shouting reverberating around the slum.
"Kereta! Kereta! (A train! A train!)," cried mothers rushing to grab children playing on the track as a roaring locomotive approached, whipping up clouds of dust and garbage as it surged towards the flimsy shacks.
A train recently claimed the life of a little girl who had run after her cat.
The slum dwellers, like half of Indonesia, live on less than US$2 a day. Each tourist pays 500,000 rupiah (about NZ$67) to visit, with half of that going to the tour company, and the rest funding doctor visits, microfinance projects or community projects such as school building.
"I don't give cash. I pay the doctors directly, for example," says Poluan.
But that does not reassure some critics.
"I'm against slums being turned into tourist spots," said Wardah Hafidz, an activist with the Urban Poor Consortium.
"It's not about shame. People should not be exhibited like monkeys in the zoo.
"What residents get from these tours, in cash or whatever form, only strips them of their dignity and self-respect, turning them into mere beggars.
"They not only become dependent on handouts, but come to expect them. It doesn't help them to believe they are capable of standing on their own two feet or getting them out of the spiral of poverty."
But slum residents say they look forward to tourists' visits.
"I like that foreigners want to know about us. It's good they want to know about us," says Djoko, a father in his fifties, as he removed labels from a pile of glass and plastic bottles before selling them for recycling.
Tourists deny charges of voyeurism, and say that what they witness inspires them to action.
"If I had not seen it, I would not have done anything about it," says Caroline Bourget.
Bourget, a teacher at Jakarta's French school, is now discussing setting up a mobile school in the slum to give disadvantaged children a better chance in life.
"Here we are at the heart of reality," she says.