World’s Deepest Underwater Railway Tunnel


150 years ago, an Ottoman sultan proposed the idea of the Marmaray tunnel, which links the east and west sides of Istanbul.

Now the 90th anniversary of the Turkish Republic will be celebrated with the world’s deepest underwater railway tunnel. The 190-foot deep, 8.5 mile long tunnel is running under the Bosporus channel after eight years of construction. The project faced a lot of unexpected troubles in its completion – its finish date got delayed by 4 years. Using the same immersed-tube method utilized in other underwater railway tunnels, the Marmaray was created section by section and is deemed the world’s deepest of its type.


It is hoped that it will be capable of carrying up to 1.5 million passengers a day, which will significantly reduce the traffic flow from the two existing bridges on either side of the city. Moreover, it is hoped that the tunnel will become a permanent part of the train route for rail travel between China and Western Europe. Structural concerns were there of course that this tunnel might get damaged by earthquakes as it’s located in a high seismic zone. However, the Turkish Transportation Minister approved as ‘the safest place in Istanbul’, a structure that can withstand earthquakes as high as magnitude of 9.0 due to the tubular structure reinforced with shock resistant flexible joints.