Iwate Ichinohe Tunnel is the 25.810 km long and also world’s eighth largest tunnel.
Iwate-Ichinohe tunnel in Japan ranks seventh among the world's longest railway tunnels. Also built as part of the Tohoku Shinkansen railway, it has an overall length of 25.81km.
The tunnel design features a single bore twin track with a horseshoe shape. It is 9.8m wide and 7.7m high in cross-section. Construction methods used included the New Austrian Tunnelling Method (NATM), drill and blast or mechanical excavation, and full face or bench cut methods.