The dachstein Ice Cave is AWESOME. It can be visited by taking the gondola up to a station and then a 10 minute walk up paved trails or one can hike from the base in Obertraun about 2 hours (I think). There is an admission charge even if one hikes up. They discourage photography inside the cave itself. Open year round I think, I was there in the summer.
Definitely something that should be on the itinerary if you're going to the Salzkammergut read more