Antilia, a 27-story skyscraper on the pricey Altamount Road in Mumbai, is the most expensive home in the world, valued at upwards of $1 billion. Mukesh Ambani, an Indian business tycoon and multi billionaire, moved into the 400,000-square-foot mansion in 2012 with his wife and three children. The modern property was designed by Chicago-based architects Perkins & Will.