Fehmarn Sound Tunnel
The 389th longest tunnel in the world
The Fehmarn Sound Tunnel is a planned tunnel between the German mainland and the Island of Fehmarn. It was projected to be built by 2028 to supplement and to relieve the Fehmarn Sound Bridge. It should cost €718 million. The tunnel will be near Großenbrode.
Tunnel data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).