The filthy and cramped 535-acre slum of Dharavi stands on prime building land in Mumbai, parts of which have some of the world's most expensive real estate, and has long been an embarrassment to promoting the country's economic capital as a global financial centre.

Newspaper advertisements were published in 20 countries Wednesday offering "the opportunity of the millennium" for five major developers to take part in the long-delayed and controversial project in one of Asia's largest slums.