Tatamiishi, Kumejima Okinawa Japan

These strange rocks on the south coast of Nishi-Ou Island, east of Kumejima Island, are a protected natural treasure of Okinawa 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.

This strange natural phenomenon is caused when Andesite-type lava gradually cools to rock, splintering can can take place 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. Tatamiishi means Tatami mat stones, named because they are spread out like a mat on the sea shore.

From Kumejima Airport: Approx, 25 min. by car
Parking: Free
Address: 170 Ou, Kumejima-cho, Shimajiri-gun, Okinawa