The Holmenkollen Ski Museum at the base of the jump is the oldest ski museum in the world, opened in 1923. Its collection covers around 4,000 years of skiing — from primitive wooden planks used by hunters in the Stone Age through to modern Olympic equipment.
The museum traces the full arc of skiing's transformation from survival tool to sport, with a particularly good section on the Nansen and Amundsen polar expeditions, both of which depended on skis. A combined ticket with the ski jump tower makes sense if you're already here — the museum takes an hour, and the context it gives to the jump above makes the view more meaningful.