Two magnificent monoliths towered over us, reaching almost to the surface. The smooth sides and clear cut corners looked surprisingly out of place in the midst of this rugged seascape. We wondered if this really was the entrance to an ancient city, now submerged beneath the waves at Yonaguni.
Too narrow to pass between, we swam around the pillars and were picked up by a strong current that swept us into the heart of this historic site.
The main spectacle appeared in front of us, a series of steps fit for a giant. Each one was at least a metre high with some stretching as far as the eye could see. The steps were cut out of the rock at perfect right angles, surely not a natural phenomenon.
As we cruised up over the top of the main terrace, we came across our final piece of evidence. This large stone, known as the turtle, had a broad body and a triangular head pointing due north, a sure sign that this was the work of an ancient civilisation. Or so we were told.
The Main Terrace
The Mystery of the Kaitei Iseki
The mysterious Kaitei Iseki (underwater ruins) of Okinawa's Yonaguni island have been the subject of considerable debate since they were discovered in 1986. Some believe that it is part of the mythical lost continent of Mu, the Asian version of Atlantis, and it has even been suggested that aliens may have been involved. However, most suspect more mundane beginnings.
A recent theory suggests it may have been a quarry. It certainly shares some similarities with ancient Egyptian quarries where square blocks and obelisks were removed as single pieces leaving behind stepped recesses in the rock.
Although there are natural examples of some of these features elsewhere, even sceptics agree that having so many occurring in such a compact area would be unlikely.
The purpose of this site, its age and how exactly it ended up several metres beneath the sea remain a mystery.
Yonaguni Travel Tips
December to February is hammerhead season in Yonaguni. Spend a few days and combine some blue water hammerhead dives with a dive on the underwater ruins.
How To Get To Yonaguni
Fly from mainland Japan to Naha.
Fly from Naha to Yonaguni. These flights can be booked through Japan Airlines.
There are several dive shops on the tiny island of Yonaguni. All arrange regular trips to the Kaitei Iseki (underwater ruins).