TWIL #038 - Japan Has Underwater Train Stations Inside a Tunnel
The Seikan Tunnel connects Japan's main islands under the sea - and for years it contained two working train stations built entirely underwater, accessible only by a special tourist train.
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The Seikan Tunnel connecting Honshu and Hokkaido, Japan, is 53.85 km long, making it one of the world's longest railway tunnels. Of that length, 23.3 km runs under the Tsugaru Strait - the stretch of sea between Japan's two main islands. At its deepest point the tunnel passes 240 metres below sea level.
Inside the undersea section, Japan built two fully operational train stations: Tappi-Kaitei (on the Honshu side) and Yoshioka-Kaitei (on the Hokkaido side). These were not maintenance facilities - they were public stations with waiting rooms, exhibition spaces, and escape hatches into the tunnel walls.
Neither station was on the standard rail route. To visit, passengers took a specially arranged excursion train that stopped in the tunnel itself, allowing tourists to walk around in rooms carved out of the seabed, well below the surface of the strait.
The stations also served an important safety function: they were designed as emergency refuge points where passengers could evacuate in the event of a tunnel fire or flood, with sealed rooms stocked with supplies.
The Seikan Tunnel opened in 1988. The tourist excursion service ran for years but was eventually discontinued - the stations are now closed to the public, used only for maintenance access. The tunnel itself continues to operate, carrying the Shinkansen bullet train under the sea since 2016.
Two train stations that exist underwater, carved into the seabed, that you can no longer visit.