The Gotthard Base Tunnel is the longest tunnel of the world, 57km long. The tunnel shortens travel distance through the Alps and reduces the number of freight trains.
The Marmaray Project consists of a suburban rail system that establishes a connection between Istanbul Halkalı and Gebze. The project interconnects the city’s European and Asian Sides by a 1387 meter long railway tunnel constructed under the Bosphorus strait. The overall length of the rail system is 76 km. The Bosphorus will be crossed by an immersed tube, assembled from 11 sections with lengths varying between 98,5 and 138 meters. With a depth of 56 meters, these tube sections will comprise the world's deepest undersea immersed tube tunnel, earthquake-proof against magnitudes of 10.