Construction work has begun on a $2.5-billion (2.1-billion-euro) project to build a rail tunnel under the Bosphorus Strait that flows through Turkey’s biggest city Istanbul.

Despite fears about the risk of earthquakes, the underwater train tunnel will run 1,600 m at 60 m below sea level.
The tunnel is due for completion by 2008. The entire project comprises a 13 km rail tunnel that includes a 1.6-km immersed tube tunnel, 11.5 km of bored and cut-and-cover tunnels and four stations.
A related commuter rail project involves upgrading 63 km of existing at-grade rail lines and a total of 37 stations on either side of the strait.
Work is led by a Turkish-Japanese consortium and the cost of the project is being supported by the Japanese Bank for International Co-operation.