Holmenkollen
The Holmenkollen is a large hill outside 
8 Oslo. It's possible to go on a train up the side of it, visit a ski jump and, if you're fortunate enough to go there in winter, tramp around on the cross country skiing trails and throw massive snowballs at Moules' head.
The hot chocolates at the top are very expensive, but there's a rule that, if you finish your drink whilst still in the queue, you can refill at no extra charge.