Hvaler Tunnel
The 259th longest tunnel in the world
The Hvaler Tunnel (Hvalertunnelen) is a subsea road tunnel which connects the island of Kirkøy to the rest of Hvaler in Østfold County, Norway. The tunnel opened in 1989 and is 3,751 meters (12, 306 ft) long and 120 meters (390 ft) deep with an incline of 10% at its steepest point, located on Norwegian County Road 108.
Tunnel data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).