Investigation Summary
1299–1304 under King Haakon V. Notable as the only major Norwegian fortress never taken by storm across seven centuries of military history. During WWII the fortress was used as a German-occupied prison and execution site; 28 Norwegian civilians were executed here on 9–10 February 1945, and Vidkun Quisling was executed here on 24 October 1945.
Paranormal claims — including the ghost dog Malcanisen and the faceless apparition Mantelgeisten — derive exclusively from tourism and commercial paranormal sources and lack any identified primary documentation. Norway's Resistance Museum is located on the grounds.