Enrei Tunnel
The 178th longest tunnel in the world
Enrei Tunnel is a tunnel on the JR's Chuo Main Line in Japan that runs from Okaya, Nagano to Shiojiri, Nagano in Nagano prefecture with approximate length of 5.994 km. It was completed and opened in 1983. Its construction took 14 years, and reduced the travel distance between Okaya and Shiojiri by about 16 km.
Tunnel data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).