Tokyo, officially Tokyo Metropolis, is one of the 47 prefectures of Japan and located on the eastern side of the main island Honshū. The twenty-three special wards of Tokyo, each governed as a city, cover the area that was once the city of Tokyo in the eastern part of the prefecture, and total over 8 million people. The population of prefecture exceeds 12 million. The prefecture is the center of Greater Tokyo Area, the world's most populous metropolitan area with 35 million people.