The Seikan Tunnel (青函トンネル
) is a 53.85 km (33.46-mile) railway tunnel in Japan, with 23.3 km (14.5 miles) under the seabed under the Tsugaru Channel
. The track level is about 140 metres (460 ft) below the seabed and 240 m (790 ft) below sea level. It travels beneath the Tsugaru Strait
connecting Aomori Prefecture on the Japanese island Honshu
and the island Hokkaido
as part of the Kaikyo Line of Hokkaido Railway Company.
Seikan is both the longest and the deepest operational rail tunnel in the world. The Gotthard Base Tunnel in Switzerland will be longer when it opens to traffic in 2017. Seikan is also the longest undersea tunnel in the world, but the Channel Tunnel between the United Kingdom and France has a longer undersea portion.