The Ogasawara Islands were once known as the Bonin Islands. The islands were formed about 48 million years ago by volcanos that built an oceanic crust. Its main islands are Chichijima ‘Father Island’ and Hahajima ‘Mother Island’ which are the only ones that are inhabited. Other islands in the chain have similar names such as Yomejima 'Bride Island', Nakodojima 'Matchmaker Island', Anijima 'Elder Brother Island', Ototojima 'Younger Brother Island' and so on. The main spots where visitors are allowed are on Chichijima and Minamijima. Although the islands are some 1000 km away, they are part of Tokyo City.