Mumbai, also known as Bombay, is the capital city of the Indian state of Maharashtra. Mumbai is the financial capital and the most populous city proper of India, with an estimated population of 12.5 million (1.25 crore). Mumbai is the centre of the Mumbai Metropolitan Region, which is among the most populous metropolitan areas in the world with a population of over 23 million. Mumbai lies on the Konkan coast on the west coast of India and has a deep natural harbour. In 2008, Mumbai was named an alpha world city. Mumbai has the highest number of billionaires of any city in Asia.