The longest and deepest operational railway tunnel in the world was opened in Japan on March 13, 1988. The Seikan Tunnel, which is 33.46 miles long with 14.5 miles of that under the seabed, connects the island of Honshu with the island of Hokkaido.

A tunnel had long been considered between the islands, especially as traffic skyrocketed after World War II, but the proposal was jump-started after a typhoon sunk five ferry boats crossing the strait and killed 1,430 people in 1954. Construction began in 1971, and it wasn’t easy. The unpredictable volcanic rock and soil prevented engineers from using a boring machine. They instead had to drill and blast through all 33 miles.

Once it opened, all freight trains used the tunnel for transport, but most passengers now opt for air travel, which is relatively fast and cheap between the islands. There is also a popular overnight luxury passenger train that is often sold out. By 2015, the high-speed bullet trains, the Shinkansen, are expected to extend to Hakodate and eventually to Sapporo.

The tunnel also houses the first stations built underwater. The two stations were to be used for emergencies, but the Tappi-Kaitei station continues to house a museum that can be visited on special tours.