administrative boundaries of Tokyo Metropolis are two island chains in the Pacific Ocean directly south: the Izu Islands, and the Ogasawara Islands, which stretch more than away from the mainland. Because of these islands and the mountainous regions to the west, Tokyo's overall population density figures far under-represent the real figures for the urban and suburban regions of Tokyo. 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. In addition to these 23 special wards, Tokyo also includes 26 more cities ( -shi), five towns ( -chō or machi), and eight villages ( -son or -mura), each of which has a local government. The Tokyo Metropolitan Government administers the whole metropolis including the 23 special wards and the cities and towns that constitute the prefecture. It is headed by a publicly elected governor and metropolitan assembly. Its headquarters is in Shinjuku Ward. Municipalities Since 2001, Tokyo consists of 62 municipalities: 23 special wards, 26 cities, 5 towns and 8 villages. Any municipality of Japan has a directly elected mayor and a directly elected assembly, each elected on independent four-year cycles. 23 of Tokyo's municipalities cover the area that had been Tokyo City until WWII, 30 remain today in the Tama area (former North Tama, West Tama and South Tama districts), 9 on Tokyo's outlying islands. The of Tokyo comprise the area formerly incorporated as Tokyo City. The special wards use the word "city" in their official English name (e.g. Chiyoda City). The wards differ from other cities in having a unique administrative relationship with the prefectural government. Certain municipal functions, such as waterworks, sewerage, and fire-fighting, are handled by the Tokyo Metropolitan Government. To pay for the added administrative costs, the prefecture collects municipal taxes, which would usually be levied by the city. The "three central wards" of Tokyo – Chiyoda, Chūō and Minato – are the business core of the city, with a daytime population more than seven times higher than their nighttime population. Chiyoda Ward is unique in that it is in