Don’t bother looking it up in the Michelin Guide. The Maze is a 20-room-plus (it keeps growing) hostel sprouting from the crown of a favela, one of the many chockablock shantytowns that cling to Rio’s mountains. The impossible jumble of raw brick and cement buildings offends the laws of gravity, not to mention the sensibilities of upscale Cariocas, as the city’s residents are called. But for moneyed gringos eager to escape the crush and clichés of mass travel, the setting couldn’t be more appealing.

And it’s not just in Brazil. Slum tours are the travel business’s new growth industry. Whether it’s in a Mumbai shantytown or the alleys of Moscow, a Mexican garbage dump or the blighted townships of Johannesburg, foreign travelers are spending time in neighborhoods they long avoided. Critics dismiss the trend as “poorism,” a peep show on poverty for the well heeled. But tour operators and their patrons say visiting the slums and coming face to face with the stark disparities of megalopolitan life—where a power lunch costs as much as a favela maid’s monthly wage—can be a transforming experience. “A porthole to a wonderful world,” one visitor wrote in the Maze’s guest book. Of course, not everything is wonderful in the slums of Rio, home to one in five of the city’s 10 million residents. But by drawing strangers to unlikely places, slum tours are working to break down the barriers that conspire to keep the poorest citizens hidden away like an ugly secret.

Few have done more for the genre than Bob Nadkarni, the Maze’s proprietor. A veteran film journalist, Nadkarni decided to move to Rio’s vertiginous favela after giving his maid a lift home there in the early 1980s. He built a house that kept getting bigger, not least because of the steady stream of friends and visitors. By early this decade, he decided to turn his home into a bed-and-breakfast and launched a monthly jazz night. Now a steady patter of Danish, French, English and Dutch can be heard from his aerie overlooking Guanabara Bay.

Not surprisingly, the film industry caught on, and now Nadkarni’s house has been used as both a base and a backdrop for a number of big studio projects, including the upcoming “The Incredible Hulk,” a Snoop Dogg music video and a handful of documentaries. In the coming months Matt Dillon and Charlotte Rampling are scheduled to trek up the hillside to shoot a comedy set partly in the Maze. Director Jonathan Nossiter even asked Nadkarni himself to play a supporting role. He won’t have to stretch himself too far: his character is a partner in a slum-tour operation.