Kigan-gun is a series of odd-shaped rocks designated as the prefectural government along the south coast of Nishi-Ou Island, east of Kume Island. More than 1,000 pentagonal and hexagonal rocks that look like turtle shells connected to each other appear at low tide. It extends north and south 50 meters and a length of 250 meters along the beach. It is also called a columnar joint that happens when the andesite lava slowly cools to become a rock. Wave erosion has worn the rocks down nearly flat over the years. Such formations are extremely rare in the world and are truly natural works of art.