Descend into the world's longest undersea tunnel — a marvel of 20th-century engineering bored 240m beneath the Tsugaru Strait — and visit the remarkable memorial museum that tells its extraordinary construction story. A rare, once-in-a-lifetime descent beneath the waters your ship is crossing.
What to expect
A private vehicle drives you to Tappi, at the northernmost tip of Honshu, where you descend by elevator to the undersea exhibition station carved into the bedrock beneath the strait. The museum displays original drilling equipment, construction photographs, and geological cross-sections of the 53.85km tunnel. Your guide narrates the 24 years of construction and the lives of the engineers who built it. Back at the surface, the rugged Tappi headland offers panoramic views of the strait and, on clear days, the Hokkaido coastline.
Good to know
Located ~2 hours from Aomori port by private vehicle — check all-aboard time carefully and allow a full day. Pre-book private transport in advance; the site is remote and not served by regular excursion buses. The underground elevator experience is not suitable for those with severe claustrophobia. Advance reservation for tunnel access is required.