In 1987, while looking for a good place to observe hammerhead sharks, a director of the Yonaguni-Cho Tourism Association, Kihachiro Aratake, noticed some singular seabed formations resembling architectonic structures off the coast of Yonaguni, the southernmost of the Ryukyu Islands, in Japan. There is an ongoing debate about whether the site is completely natural, a natural site that has been modified or a man-made artifact.