Yonaguni Monument - Manmade ancient Rock underwater
The Yonaguni Monument is a massive underwater rock formation off the coast of Yonaguni, the southernmost of the Ryukyu Islands, in Japan, 110 km east of Taiwan.
The rock was discovered by Diver Kihachiro Aratake. There is a debate about whether the site is completely natural, is a natural site that has been modified, or is a manmade artifact.
In 1987, while looking for a good place to observe the sharks, Kihachiro Aratake, a director of the Yonaguni-Cho Tourism Association, noticed some singular seabed formations resembling architectonic structures.[3] Shortly thereafter, a group of scientists directed by Masaaki Kimura of the University of the Ryūkyūs visited the formations. Kimura is a strong advocate of the view that the formations are artificial.
Supporters of artificial origin argue that, while many of the features seen at Yonaguni are also seen in natural sandstone formations throughout the world, the concentration of so many peculiar formations in such a small area is highly unlikely. They also point to the relative absence of loose blocks on the flat areas of the formation, which would be expected if they were formed solely by natural erosion and fracturing.
If any part of the Monument was deliberately constructed or modified, that must have happened during the last Ice Age, when the sea level was much lower than it is today (e.g. 39 m (130 ft) lower around 10,000 years BCE).