Yonaguni Monument

The Yonaguni Monument is an underwater rock formation lying 25 metres below the surface off Yonaguni's southern coast, and it is the island's most famous and most debated attraction. The structure consists of layered sandstone terraces, platforms, columns, and what appear to be steps — carved-looking features that have generated intense controversy about whether they are natural or man-made. Whether you believe it is the remnant of an ancient lost civilisation or simply a remarkable geological formation, diving around it is an extraordinary experience.

The monument is accessible only by diving or snorkelling — there is no way to see it from the surface. Local dive operators in Yonaguni village offer guided dives to the site, and the visibility in the clear subtropical water is usually excellent. Snorkellers can reach the shallower portions in calm conditions. The current around the monument can be strong; going with a local guide is strongly recommended.

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A story
The monument was discovered in 1987 by local diving instructor Kihachiro Aratake while searching for hammerhead sharks. The discovery sparked immediate controversy that continues today: geologist Masaaki Kimura spent years measuring and documenting the structure and argued it was a man-made megalith from a civilisation that existed before the end of the last Ice Age, when sea levels were lower and the site was above water. Other geologists maintain it is entirely natural, created by the fracturing patterns of the sandstone. No consensus has been reached.