The Seikan Tunnel(Ja:青函トンネル)is a railwaytunnel in Japan.[1] It connects Hokkaido to Aomori Prefecture.[2][3] This tunnel is the second longest transport tunnel in the world. The tunnel is 53.85 km (33.49 miles) long.[4] 23.3 km (14.5 mile) of the tunnel is underwater. There are two stations in the tunnel.[3]