Shinjuku ( Japanese: 新宿区, Hepburn: Shinjuku-ku, IPA: [ɕiɲdʑɯkɯ] ^ⓘ), officially called Shinjuku City, is a special ward of Tokyo, Japan. It is a major commercial and administrative center, housing the northern half of the busiest railway station in the world ( Shinjuku Station) as well as the Tokyo Metropolitan Government Building, the administrative center of the Tokyo Metropolitan Government. , the ward has an estimated population of 346,235 and a population density of 18,232 people per km². The total area is 18.23 km². Since the end of World War II, Shinjuku has become a major secondary center of Tokyo ( fukutoshin), rivaling the original city center in Marunouchi.