The Yonaguni Monument is a massive rock monument discovered off the coast of Yonaguni island. There is a debate about whether the site is completely natural, is a natural site that has been modified, or is a manmade artifact but the pics are very clear! It seems unlikely the natural origin of those one for example:
The sea off Yonaguni is a popular diving location during the winter months owing to its large population of hammerhead sharks. 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. Shortly thereafter, a group of scientists directed by Masaaki Kimura of theUniversity of the Ryūkyūs visited the Monument.
The formation has since become a relatively popular attraction for divers in spite of the strong currents. In 1997, Japanese industrialist Yasuo Watanabe sponsored an informal expedition comprising writers John Anthony West and Graham Hancock, photographer Santha Faiia, geologist Robert Schoch, a few sport divers and instructors, and a shooting crew for Channel 4 and Discovery Channel. Another notable visitor was freediver Jacques Mayol, who wrote a book on his dives at Yonaguni.
Tool marks and carvings have been discovered upon the stones (and documented) which indicate that they have were constructed rather than being natural stone structures.
Masaaki Kimura, a marine geologist from Japan’s Ryukyus University, Japan has been studying and mapping the site for over 15 years and believes that the site is over five thousand years old – but was sunk during an earthquake two thousand years ago.
Others have estimated that the structure is far older – including Teruaki Ishii, professor of geology at Tokyo University who determined that the submergence occurred at the end of the last ice age – which was around ten thousand years ago (over twice as old as the pyramids in Egypt) – If this is the case, then our history books would have to be revised to take into account an advanced Eastern culture, more advanced than any early Western culture.