Festning Tunnel
road tunnel in Oslo, part of the Opera Tunnel
The Festning Tunnel (Norwegian: Festningstunnelen) is a motorway tunnel on European Route E18 in the city center of Oslo, Norway. The tunnel has two tubes, with three lanes in each. It runs from Bjørvika, under Akershus Fortress, The City Hall Square and Vika to Filipstad. The tunnel is 1,800 metres (5,900 ft) and −45 m (−148 ft) elevation at the deepest.
The tunnel was previously also known as the Mountain Line (Fjellinjen) and the Oslo Tunnel (Oslotunnelen). The name Fjellinjen was since taken over by the company responsible for charging toll fees 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 240 million kr.
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.
The public source identifies “Festning Tunnel” as road tunnel in Oslo, part of the Opera Tunnel. This brief keeps that definition visible, then builds a research path around Festning, Tunnel and road.
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Attribution, date and provenance are strongest when supported by the original work, a catalogue record and documented transmission. The source revision retrieved here is dated Jul 24, 2026. The linked authority identifier is Q4590657. Authority coordinates are 59.910, 10.730. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank. The first chronological checks are 1998, 2008 and 2009.
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This entry incorporates text from “Festning Tunnel” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.