Wikipedia
Tingstadstunneln
Tingstadstunneln (Tingstad Tunnel) is a motorway tunnel under the Göta älv, connecting Hisingen with mainland Gothenburg. The tunnel was constructed with two parallel immersed tubes with three lanes of traffic in each tube. It is part of the E6 route linking Norway with south-west Sweden.
Construction started on 17January 1961, and the tunnel was inaugurated at 11:30 am on 29March 1968.
The tunnel has the lowest motorway elevation in Sweden, at below sea level (nearby Götatunneln is lower and designed like a motorway but not signposted as one).
The tunnel has severe traffic congestion problems since several years, so therefore a new tunnel is built a little farther north, Marieholmstunneln, to be opened in 2017.