The population of Greater Tokyo has a estimated at 35 million people. This is the largest metropolitan area in the world in terms of population greatly exceeding Mexico City with the next highest population of 19 million. It should be noted that the actual city of Tokyo itself has approximately 12 million people. Tokyo is basically many extremely large cities that are conjoined to the extent that is difficult to tell where one ends and the other begins. To give an example, Yokohama is basically interconnected to Tokyo and has a population the size of the city of Chicago.