One of the most appalling and fascinating aspects of Sao Paulo and Rio de Janeiro here in Brazil are the so-called "favelas". The Brazilian equivalent of a shanty town, these have generally grown up on public land right alongside much more affluent areas. While mired in poverty, they are also hotbeds of entrepreneurs, with highly localized economies, creative solutions to infrastructure problems, and even profit-making tours offered of some of the larger favelas.
Here is a view of Favela Morumbi, one of the largest such zones here in Sao Paulo. Something like 19% of the population of Rio de Janeiro lives in favelas, and a smaller number here in Sao Paulo.
More here in the NYT on the "poor-ism" and the controversies around organized favela tours