Under Japanese law, the prefecture of Tokyo is designated as a , translated as ''metropolis''. Tokyo Prefecture is the most populous prefecture and the densest, with ; by geographic area it is the third-smallest, above only Osaka and Kagawa. Its administrative structure is similar to that of Japan's other prefectures. The , which until 1943 constituted the city of Tokyo, are self-governing municipalities, each having a mayor, a council, and the status of a city.