The 20th century changed the way we live. Human population went up from 1.5 billion in 1900 to 7 billion in 2010. The hope of a better life drove--and continues to drive--people to urban areas, leading to the growth of megacities around the world.In India, just three metropolises--New Delhi, Mumbai and Kolkata--support a total population of 55 million and feature among the ten most populated cities on Earth. Between 2015 and 2030, India's GDP is expected to multiply five times, with over 7...