Lowest railway line

The Seikan Tunnel, which crosses the Tsugaro Strait between Honshu and Hokkaido, Japan, reaches a depth of 240m 786ft below sea level. The tunnel was opened on 13 Mar 1988 and is 53.85km 33.46miles long. Trains stop in the middle of the Seikan Tunnel for two minutes so that passengers can take pictures through the windows of panels on the walls of the tunnel.  By comparison, the channel tunnels linking Dover to Calais is at an average depth of 45 m (148 ft) below the sea floor.