Seikan Tunnel, Underwater railway tunnel between Honshu and Hokkaido, Japan
The Seikan Tunnel is an undersea railway connection stretching 53.85 kilometers and linking Honshu to Hokkaido through the Tsugaru Strait. The route runs deep below the water and allows train traffic between the two main islands of Japan.
Work began in 1971 after a typhoon in 1954 led to ferry accidents in the strait, and was completed in 1988. The construction took nearly two decades and required considerable technical effort.
Passengers experience the crossing between islands as part of their journey through Japan, with the tunnel closing the gap between the regional character of Honshu and Hokkaido. Many travelers use it to reach northern areas where landscape and climate differ noticeably.
Daily passenger and freight trains run through the route, with two underground stations offering emergency systems and maintenance facilities. Travelers usually notice the passage only through changes in pressure and dimmed light during the ride.
At the deepest point the route sits 240 meters below sea level, while the tracks run 140 meters beneath the seabed of the Tsugaru Strait. This double depth provides stability and safety against seismic movement and ocean currents.
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