Yonaguni Monument

The Yonaguni Monument is a submerged rock formation off Yonaguni Island, Japan, discovered by diver Kihachiro Aratake in 1986. The rectangular structure measures over 50 metres long and 20 metres wide, with flat surfaces and sharp edges resembling a stepped pyramid. Marine geologist Masaaki Kimura argues it is a man-made monolith, while geologists like Robert Schoch attribute its shape to natural weathering of sandstone along parallel bedding planes and joint fractures. Neither the Japanese Agency for Cultural Affairs nor Okinawa Prefecture recognises it as a cultural artifact.