Projected Population in 2015: 15.2 million
Population in 2005: 12.4 million

Along with five other megacities on this list, Dhaka was associated with a part of the British Empire. (The others are Mumbai, New York, Shanghai, Delhi and Calcutta.) Earlier, Dhaka had belonged to the Mughal Empire; nowadays, it's the capital of Bangladesh, a Muslim nation that used to be part of Pakistan. (Pakistan's current largest city, Karachi, fell just short of this Top 10, coming in at No. 12.)