Marmaray project continues at full speed. The most intriguing and interesting part of the project which will connect Gebze and Halkali with a undersea commuter train line is definitely the sunken tube tunnel constructed under the Strait. The construction of the world’s deepest tube tunnel built 60 meters below the sea level has been completed and the track laying process has started. The 1.4 km tunnel for which 1 million cubic meter dirt, gravel and rock have been dug up consists of 11 elements. These elements which are placed carefully into the trench ditched on the sea floor are connected 60 meters below the surface.