Curious underwater structures off Yonaguni and a further five related structures off the main island of Okinawa. In total the alleged ruins cover an area spanning 984 feet by 492 feet (300 meters by 150 meters). The top is about 5 m below sea level. The complex looks very similar to the numerous ancient stone quarries of South America. A pancake stone structure(s?) is found on shore near Yonaguni and it is possible that they are related to the underwater ruins.