Largest Urban Agglomerations (Megacities) of the World A megacity is usually defined as a metropolitan area with a total population in excess of 10 million people. Some definitions also set a minimum level for population density (at least 2,000 persons/square km). A megacity can be a single metropolitan area or two or more metropolitan areas that converge. The terms conurbation, metropolis and metroplex are also applied to the latter. The terms "megapolis'" and megalopolis are sometimes used synonymously with megacity, though those terms denote a semi-continuous chain of large metropolitan cities. As of 2011, there are over 20 megacities in existence -- with conurbations such as Mumbai, Tokyo, Seoul, New York City, Mexico City and Karachi having populations in excess of 20 million inhabitants each. In the 2000s, the largest megacity is the Greater Tokyo Area. The population of this urban agglomeration includes areas such as Yokohama and Kawasaki, and is estimated to be between 35 and 36 million. This variation in estimates can be accounted for by different definitions of what the area encompasses. While the prefectures of Tokyo, Chiba, Kanagawa, and Saitama are commonly included in statistical information, the Japan Statistics Bureau only includes the area within 50 kilometers of the Tokyo Metropolitan Government Offices in Shinjuku, thus arriving at a smaller population estimate. A characteristic issue of megacities is the difficulty in defining their outer limits and accurately estimating the populations. By 2025, according to the Far Eastern Economic Review, Asia alone will have at least 10 megacities, including Mumbai, India (33 million), Shanghai, China (27 million), Karachi, Pakistan (26.5 million), Dhaka, Bangladesh (26 million) and Jakarta, Indonesia (24.9 million people). Lagos, Nigeria has grown from 300,000 in 1950 to an estimated 12.5 million today, and the Nigerian government estimates that the city will have expanded to 25 million residents by 2015. Lahore, Pakistan will also be a megacity in 2025. For more info: http://en.wikipedia.org/wiki/Megacity For more Top Ten Videos: http://www.youtube.com/user/theultimatetopten/