The Yonaguni Monument, an enigmatic underwater structure near Japan’s Yonaguni Island ... that the monument was once part of a sprawling city or religious site that later became submerged ...

Japan boasts the world's longest underwater tunnel, which stretches for more than miles under the seabed of the Tsugaru Strait, but it's now barely being used. Work on the Seikan Tunnel was completed ...

A total of about 19km of sewage pipes managed by the Tokyo metropolitan government are set to be inspected. The pipes are ...