What Fortress used as a palace and prison has the Festning tunnel running underneath it?
Festning 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 1800 m and -45 m elevation at the deepest.
Svartholm fortress The Svartholm fortress (Finnish: "Svartholman merilinnoitus" ; Swedish: "Svartholms fästning" ) was built between 1749 and 1764 outside Loviisa in Southern Finland by Augustin Ehrensvärd. The fortress, which lies at the mouth of the Bay of Loviisa, along with the planned land fortress at Loviisa, would have prevented invading Russian forces from entering what was then Swedish territory in present-day Finland.