Credits : Wikipedia
'Seikan tunnel' as you can see in the above pic, is the Longest tunnel in the World. It also holds the record for the Deepest operational tunnel in the World (for railways only). For the deepest tunnel in the world in general go here -
Eiksund Tunnel - The deepest tunnel in the World
Facts About Seikan Tunnel
Seikan tunnel is nearly '53.85 kilometer long' with a 23.3 kilometer section under the sea-bed which has been continuously welded. The track is 460 ft(140 meters) below the seabed and total depth from sea level to the tracks is 240 meters (790 ft).
The construction of Seikan tunnel was decided because of increasing number of ferry traffic between the two islands to which this tunnel connects. In 1971, based on estimations and safety - decision was made to construct a long 53 kilometers of railway track beneath the sea to connect those thriving cities together. All-in-all 34 construction personnel perished due to geological conditions.
Finally with all those brutal conditions, the Seikan tunnel was opened on 13 March 1988 and the cost of construction reached 3.6 billion Dollars.
Records set by Seikan Tunnel
Seikan Tunnel holds the record for Deepest operational Railway Tunnel in the World and also as the longest Tunnel in the World.
Also read : Deepest Cave in the World ( 2kms Deep)