These strange rocks on the south coast of Nishi-Ou Island, east of Kume Island, are protected by the Prefecture. The rocks emerge at low tide. They look like pentagonal and hexagonal turtle shells, thus they are also called the “turtle shell rocks.” There are more than 1,000 of them spread along the beach for 250 meters and back inshore 50 meters. When Andesite-type lava gradually cools to rock, it can splinter along what are called columnar joints. Such formations are extremely rare in the world. Wave erosion has worn the rocks down nearly flat. Now they look like natural works of art.