Viking fans will feel right at home at this impressive ceremonial hall, built by King Håkon Håkonsson in 1247–61 and completed for his son's wedding and coronation. Spread over three floors, it's been much restored, but the highlight is the large feasting room on the top floor, where lavish banquets would have been held.
The roof was blown off in 1944 thanks to the explosion of a Dutch munitions boat, but careful restoration work has brought the building back to its stately self. There are hourly guided tours in summer.