Review: Mumbai formerly known as Bombay, is the capital of the state of Maharashtra, the most populous city of India, and by some measures the most populous city in the world with an estimated population of about 13 million.Mumbai is the commercial and entertainment capital of India, and houses important financial institutions, such as the Reserve Bank of India (RBI), the Bombay Stock Exchange (BSE), the National Stock Exchange of India (NSE) and the corporate headquarters of many Indian companies.