The Seikan Tunnel (青函トンネル Seikan Tonneru or 青函隧道 Seikan Zuidō) is a 53.85 km (33.46 mi) railway tunnel in Japan, with a 23.3 km (14.5 mi) long portion under the seabed. The track level is about 100 metres (330 ft) below the seabed and 240 m (790 ft) below sea level. It travels beneath the Tsugaru Strait — connecting Aomori Prefecture on the main Japanese island of Honshu with the northern island of Hokkaido — as part of the Kaikyo Line of Hokkaido Railway Company (JR Hokkaido).