Loarre
One of the best Romanesque castles in Europe recently the site for Ridley Scott's film, Kingdom of Heaven just has a one-man bar hidden behind a few rocks, and a part-time guide. Close to Huesca city.Although you might be attracted to the high Pyrenees, you should definitely visit the pre-Pyrenees - a parallel range just to the North of Huesca city.
The Sierra de Guara for mountaineering and birdwatching vultures and birds of prey.