Dharavi is the largest slum in the world, with 1 million people crammed in just 100,000 dilapidated homes. 80 people sharing a single toilet and a slum housed in an area that's roughly the size of 300 football fields. The informal economy adds nearly 1 billion dollars to the Indian GDP. Dharavi will soon be replaced by multi-story buildings, glamorous shopping malls and glass walled office buildings over the next 17 years.