The sprawling Akershus Castle and Fortress is a great place to discover Oslo’s history. The major complex was begun in 1300, finished in 1308 and extended through the 17th century.
It was built principally to defend the city against attack from Sweden. State events are still held in the beautiful ballrooms and the grounds provide the venue for summer concerts and theatrical performances. The Royal Chapel and Royal Mausoleum are open to the public.

Related: The Swedish Invasion of Norway
In the fortress, the Armed Forces Museum covers Norwegian military history from the Viking period on, and provides a fascinating insight into Norway’s relationship with neighboring Denmark and Sweden over the centuries.
Related: The Haunted Attractions in Oslo

Just outside the castle, the Norway Resistance Museum, located at the place where Resistance members were executed by the Gestapo, gives a clear and detailed account (with English labels) of the mense and moving story of occupied Norway.
The Akershus Complex in Oslo, written by Tor Kjolberg