The Yonaguni Monument
Under the sea off a small Japanese island lie great stone terraces and steps that look as if they were carved.
What was reported
In 1986, a diver off Yonaguni, Japan's westernmost island, found a large underwater rock formation with flat terraces, sharp right angles and what look like steps. It lies between a few metres and about 25 metres below the surface.
A marine geologist from the University of the Ryukyus, Masaaki Kimura, studied it for years and argued that it was shaped by people, perhaps when sea levels were lower thousands of years ago.
Explanations offered
Most geologists think it is natural. The local sandstone splits along straight, parallel lines, which can produce flat surfaces and steps. Robert Schoch, a geologist who dived there, concluded it was natural, though perhaps altered by people. No tools or other clear signs of human work have been found.
- When
- Found in 1986
- Where
- Off Yonaguni Island, Okinawa, Japan
- Witnesses
- Divers and geologists
- Status
- Disputed
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.