Built in the 1290s, Akershus Festning perches majestically over the Oslo Fjord. There are numerous things to do and you could easily spend an entire day taking them all in. The gardens and ramparts are a great place to spend some time admiring harbor views before exploring the little church where King Håkon VII (1872-1957) is buried, the medieval defensive ramparts, and the halls large and small. Also on the grounds is the Norwegian Home Front Museum, also known as the Norway's Resistance Museum (Norges Hjemmefrontmuseum). Coming here means learning a lot about the German occupation, which lasted from 1940 to 1945. Guided tours of the fortress are available during the warm-weather months. 

It's part of Tripatini member Dayna Stephens's post 5 of Oslo's Top Attractions.