The Festning Tunnel is a motorway tunnel

Tunnel

A tunnel is an underground passageway, completely enclosed except for openings for egress, commonly at each end.A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers...

 on European Route E18

European route E18

European route E18 runs from Craigavon in the United Kingdom to Saint Petersburg in Russia, passing through Norway, Sweden, and Finland. It is about 1,890 km in length.-United Kingdom:...

 in the city center of Oslo

Oslo

Oslo is a municipality, as well as the capital and most populous city in Norway. As a municipality , it was established on 1 January 1838. Founded around 1048 by King Harald III of Norway, the city was largely destroyed by fire in 1624. The city was moved under the reign of Denmark–Norway's King...

, Norway

Norway

Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

. The tunnel has two tubes, with three lanes in each. It runs from Bjørvika

Bjørvika

Bjørvika is a neighborhood in the Sentrum borough of Oslo, Norway. The area is an inlet in the inner Oslofjord, situated between Gamlebyen and Akersness. It serves as an outlet for the river Akerselva. Since the 2000s, it has been undergoing urban redevelopment, being transformed from a container...

, under Akershus Fortress

Akershus Fortress

Akershus Fortress or Akershus Castle is a medieval castle that was built to protect Oslo, the capital of Norway. It has also been used as a prison.- Construction :...

, The City Hall Square

The City Hall Square, Oslo

Rådhusplassen is a square located between Oslo City Hall and the Oslofjord in Vika, Oslo, Norway. Previously used as a road and part of European route E18, it has since 1994 served as a recreational area...

 and Vika

Vika, Oslo

Vika is a neighborhood in the borough Frogner in Oslo, Norway. It is located between the Oslofjord, Aker Brygge, Pipervika, Slottsparken and Oslo City Hall....

 to Filipstad

Filipstad, Norway

Filipstad is a neighborhood in the borough Sentrum in Oslo, Norway. It serves as a container port for Oslo.The neighborhood grew from a single property, named after the pharmacist Philip Moth around 1650 - the last element is stad m 'farm'...

. The tunnel is 1800 metres (5,905.5 ft) and -45 m elevation at the deepest.

The tunnel was previously also known as the Mountain Line and the Oslo Tunnel . The name Fjellinjen

Fjellinjen

Fjellinjen AS is a municipal company owned by the City of Oslo and Akershus County Municipality . It is responsible for the collection from the toll ring around Oslo, with a total of nineteen toll plazas.-History:...

 was since taken over by the company responsible for charging toll fees

Toll road

A toll road is a privately or publicly built road for which a driver pays a toll for use. Structures for which tolls are charged include toll bridges and toll tunnels. Non-toll roads are financed using other sources of revenue, most typically fuel tax or general tax funds...

 on the urban toll ring in Oslo. The tunnel changed its official name from the Oslo Tunnel to the Festning Tunnel in 1998 to avoid confusion with the railway tunnel with the same name. In 2008 and 2009, the electrical installation in the tunnel is being upgraded, financed through toll fees, costing .

In the west, the tunnel connects to Dronning Mauds gate with a cloverleaf intersection, and also has the intersection prepared for a future Slottspark Tunnel. In the east, it connects to Nylandsveien and Ring 1 at Bjørvika. In 2012, the Bjørvika Tunnel

Bjørvika Tunnel

The Bjørvika Tunnel is a motorway immersed tunnel on European Route E18 in the city center of Oslo, Norway. The tunnel has two bores, with three lanes in each...

 will be constructed below Bjørvika, and the new tunnel will connect directly with the Festning Tunnel.

The tunnel was built to remove traffic from The City Hall Square, the square in front of the Oslo City Hall

Oslo City Hall

Oslo City Hall houses the city council, city administration, and art studios and galleries. The construction started in 1931, but was paused by the outbreak of World War II, before the official inauguration in 1950. Its characteristic architecture, artworks and the Nobel Peace Prize ceremony, held...

, and allow better access to the waterfront from the city. After the tunnel opened in January 1990, cars remained on The City Hall Square until 1994. In 1995, the Vika Line

Vika Line

The Vika Line is a light rail section of the Oslo Tramway in Oslo, Norway. It runs between Wessels plass, through the neighborhood of Vika and Aker Brygge, before arriving at Solli. The section is served by SL79 trams on line 12...

 of the Oslo Tramway was built across the square.