Austria
This fortress sits on a cliff 400 feet above the city of Salzburg. Walk up mostly for the spectacular views over Salzburg and wander the mildly interesting exhibits on war.
France
One of the best activities in Collioure is a hike up to both the stone windmill and Fort St. Elme which offers you unparalleled views of the seaside town and bay. Try to avoid doing this hike in the peak of the day when the sun can be brutal.