One of the best experiences of my trip to India was a tour of the
Dharavi Slum in Mumbai (by Reality Tours). The guy giving our tour was a college student who grew up and still lives in one of the other Mumbai slums. asked that we not take photos on the tour, but you can view some photos
here,
here,
here, and here. A few scenes from
Slumdog Millionaire were filmed in Dharavi.