is a large artificial island in Tokyo Bay, Japan, across the Rainbow Bridge from central Tokyo. It was initially built for defensive purposes in the 1850s, dramatically expanded during the late 20th century as a seaport district, and has developed since the 1990s as a major commercial, residential and leisure area. Odaiba, along with Minato Mirai 21 in Yokohama, are two of the only places in the Greater Tokyo Metropolitan area where the seashore is accessible, and not blocked by industry and harbor areas.