What Train tunnels?

* Channel Tunnel: The Channel Tunnel, also known as the Chunnel, is a 50.5-km (31.4-mile) undersea rail tunnel that connects Folkestone, Kent, in the United Kingdom, with Coquelles, Pas-de-Calais, near Calais, in northern France, beneath the English Channel at the Strait of Dover. It is, in aggregate length, the second longest rail tunnel in the world.

* Seikan Tunnel: The Seikan Tunnel is a 53.85-km (33.46-mile) undersea rail tunnel in Japan that connects the islands of Honshu and Hokkaido. It is the world's longest undersea rail tunnel, passing through the Tsugaru Strait.

* Gotthard Base Tunnel: The Gotthard Base Tunnel is a 57.1-km (35.5-mile) rail tunnel in Switzerland that runs through the Saint-Gotthard Massif of the Alps and connects Erstfeld in Uri with Bodio in Ticino. It is part of the Gotthard Axis that provides the railway route through the Swiss Alps, from Basel–Zurich to Chiasso-Milan.

* Brenner Base Tunnel: The Brenner Base Tunnel is a 64-km (39.8-mile) under-construction rail tunnel that will connect Austria and Italy through the Alps. It will be the world's longest railway tunnel once completed.

* Lötschberg Base Tunnel: The Lötschberg Base Tunnel is a 34.6-km (21.5-mile) rail tunnel in Switzerland that cuts through the Bernese Alps, connecting Kandersteg with Goppenstein. It forms part of the Lötschberg line between Bern and Brig.