Norwegian stave churches are awesome: multi-level wooden, medieval churches; highly decorated and realized in a special ‘post and lintel’ structure. You can find them throughout Norway and there are only two ones outside the country: one in Hedared, Sweden and one which was moved to Karpacz, Poland. If you want to discover one at Oslo, you should visit the Folkemuseet on Bygdøy island. It is an open-air museum exhibiting buildings from all regions of Norway. The stave church there was relocated from Gol in the Viken province of Norway.
The Norsk Folkemuseum was already created in 1894 – by that time Oslo was still named Kristiania. It was meant to collect all about the Norwegian culture and was extended continuously over time. Today it not only shows residential houses from all over Norway, there are also a historic supermarket, an ancient pharmacy, a gas station and different collections that can be visited. You can reach the museum by bus (#30), but the best connection is probably by boat: the Bygdøy ferry boat starting in front of the Rådhuset brings you easily to the museum. You just need to walk a bit from the Dronningen stop (800 meters).
Folkemuseet / Norsk Folkemuseum