Just south of Bagn you'll find Bagn Bygdesamling, an open-air museum on the banks of the river Begna. It was founded in 1920 by Olaus Islandsmoen, who was quite a character.
Olaus was a teacher, politician, and tireless cultural activist. He served as a Member of Parliament for the Radical People's Party from 1916 to 1918, and was instrumental in establishing the State Archives in Hamar. But his real passion was preserving local culture. He started the museum on his family farm, collected buildings and artefacts from around the valley, and donated the whole thing to the local community in 1939. He was also chairman of Noregs Mållag, the organisation promoting Norwegian language, and helped establish the Hadeland Folk Museum as well. People described him as the centre of any festive gathering, someone who spread joy wherever he went.
The museum now has 19 historic buildings, including a working sawmill, a watermill, and an old school with its original interior. There are also exhibitions about two other notable locals: Olaus' younger brother Sigurd Islandsmoen, a composer who spent 45 years as organist in Moss and wrote several large-scale choral works, and the wilderness author Mikkjel Fønhus, who grew up nearby and set many of his nature novels in these forests and the Vassfaret wilderness area.
There's also an exhibition about the fighting in Bagn in April 1940. This was one of the hardest battles of the Norwegian campaign. On 18 April, 1,600 German soldiers marched into Bagn and were ambushed by 500 Norwegian soldiers positioned in the hills above. The Norwegians fought so effectively that the Germans retreated ten miles back towards Hønefoss. Over the following days, 157 Germans were killed – one of their heaviest losses on Norwegian soil. The nearby Bagnsbergatn farm, where some of the fiercest fighting took place, is now a preserved national war memorial and part of the museum.
The museum is only open during summer and for special events the rest of the year. Check the Valdresmuseum website for current opening hours.