Turkey is in the midst of building a rail tunnel and a vehicle tunnel that will connect Asia and Europe through the Bosporous Strait. While the rail tunnel is expected to be completed in 2009, the vehicle tunnel will be taking bids shortly, and its expected completion date is 2011.
Rail Tunnel - the Marmaray
Of the total 13.5 km of the rail tunnel length, 1.5 km will be submerged as deep as 180 feet under the water.
The rail tunnel is called the Marmaray, and will enable travelers to travel via the rapid transit system between the western and eastern sides of Istanbul, a city which is half in Europe and half in Asia.
When completed, the tunnel will likely increase the fraction of trips in Istanbul made by rail transport from 3.6% to 27.7%. That would make Istanbul's rail transport fraction the third highest in the world, after Tokyo (60%) and New York City (31%).
While an impressive feat of engineering, the Marmaray won't hold any records for the longest or deepest tunnel in the world. (Both of those titles go to the Seikan tunnel in Japan, which is 33.5 miles long and 787 feet deep.) What's most impressive about the Marmaray, however, is that it will be earthquake- resistant since it's being built on the site of an earthquake zone. Seismic experts predict that the nearby North Anatolian Fault has a 62% chance of generating an earthquake in the next 30 years.
In order to withstand such a disaster, the 1.5-km (1-mile) part of the tunnel under the water will be flexible. The tunnel will consist of sections of tube joined together with thick rubber joints, reinforced with steel plates. This construction should enable the tunnel to absorb earthquake vibrations without breaking.
The newer vehicle tunnel will eventually be two stories tall and have four lanes. Drivers will pay about av$4 toll for a one-way trip through the tunnel.
via: Popular Mechanics and The New Anatolianv (and thanks to Emre, below!)