Akershus Fortress, the Resistance Museum and Kvadraturen

Jutting out into the harbour on a steep gneiss headland between Bjørvika and City Hall Square stands Akershus Fortress (Akershus festning). Begun in 1299 by King Håkon V Magnusson when he moved Norway's capital from Bergen to Oslo, this medieval castle withstood every foreign siege across five centuries before King Christian IV remodelled it into a Renaissance royal residence in the early 1600s and surrounded its base with stone star-shaped artillery bastions.

Walking the Fortress Grounds, Castle Halls and Museums

The outer cobbled grounds, grassy ramparts, carp ponds and cannon lookouts of Akershus Fortress are completely free to walk through every day throughout the day, offering quiet green lawns and high views over the cruise ships and island ferries below. Three distinct interiors inside the walls reward a closer look:

• Akershus Castle (Akershus slott): enter the medieval and Renaissance core to walk through the subterranean dark stone dungeons (including the Jomfrutårnet), the 14th-century Banqueting Hall (Romerikssalen), the Castle Church and the subterranean Royal Mausoleum, where white marble and green sarcophagi hold Norway's modern monarchs King Haakon VII, Queen Maud, King Olav V and Queen Märtha.
• Norway's Resistance Museum (Norges Hjemmefrontmuseum): housed in a 17th-century stone building right beside the spot where Norwegian patriots were executed during World War II, this deeply moving chronological exhibition documents the five years of German occupation from April 1940 to liberation in May 1945 through clandestine radios, underground newspapers and the sabotage of the Telemark heavy-water plant.
• The Armed Forces Museum (Forsvarsmuseet): situated in the large 1860s brick arsenal in the lower fortress courtyard (with free entry), covering Norwegian military history from the Viking Age to modern peacekeeping.

Kvadraturen and Christiania Torv

Exit the northern gate of the fortress into Kvadraturen ("The Quadrature"), the grid of right-angled streets laid out by King Christian IV after a devastating three-day fire destroyed wooden medieval Oslo in August 1624. At the heart of the grid sits Christiania Torv, framed by the 1626 yellow brick Rådmannsgården and the 1641 old City Hall around a bronze fountain sculpture of the king's gloved right hand pointing to the ground where he declared, "Here the new town shall lie."