There are many rocks and reefs on the shoreline of Numashima, and on the southeast coast, a towering giant rock Kamitategami-Iwa (上立神岩) with a height of about 30 metres which looks like a spear, has become a reminiscent symbol and icon that became the origin of the Birth of the Japanese nation: (kamiumi). This rock, which appears as in mythology, is also called Ame-no-mihashira (天の御柱, the Pillar of Heaven) and is said to be the one Izanagi and Izanami descended to.