The elephant has awoken. Bombay, India's gateway to the West, has reinvented itself - and emerged as Mumbai, a modern, self-confident commercial metropolis. A magnet for the hopes of the rich and poor. But with thousands of migrants pouring in every day, half of its almost 20 million inhabitants is forced to live in slums, between the cracks of the official city. The biggest of these slums is called Dharavi. With an estimated 800,000 inhabitants, it is one of the most densely populated areas in the world. Once Dharavi was outside the city limits. Nowadays it's at the heart of a constantly growing metropolis, flanked by traffic arteries and right next door to Mumbai's new financial hub. The former marsh has turned into prime real estate - a playground for ambitious urban planning. Ten years ago, US-trained architect Mukesh Mehta has come back to India to usher in a new turn in Mumbai's slum rehabilitation policies. His formula is Public Private Partnership.