Deep in the sea near Japan, the ruins of a city built by a lost civilization thousands of years ago have been discovered. Referred to as "Japan's Atlantis," the stone structures were located in Yonaguni Jima, Japan's westernmost inhabited island, as reported by National Geographic. An earthquake submerged the ancient city 2,000 years ago, according to the outlet.

Mysterious Tales of Japan's Atlantis

In 1987, a local diver exploring off the coast of the Ryukyu Islands rediscovered the site when they spotted a series of almost perfectly carved steps with straight edges. According to a UK media report, the rectangular, stacked pyramid-like monument was part of a long-lost Pacific civilization, possibly built by Japan's prehistoric Jomon people who inhabited these islands as early as 12000 BC. Some experts, however, compared it to Northern Ireland's Giant's Causeway, where thousands of interlocking basalt columns (all natural formations) were created by a volcanic eruption millions of years ago.

The underwater structure had arched entrances and narrow passageways, and it was attached to a larger rock mass, according to the UK media report. "I'm not convinced that any of the major features or structures are manmade steps or terraces, but that they're all-natural," said Robert Schoch, a professor of science and mathematics at Boston University who had dived at the site, reported National Geographic. "It's basic geology and classic stratigraphy for sandstones, which tend to break along planes and give you these very straight edges, particularly in an area with lots of faults and tectonic activity," he added. The structure courted enough controversy about its origin, but neither the Japanese government's Agency for Cultural Affairs nor the government of Okinawa Prefecture recognized the remains off Yonaguni as an important cultural property.