Salto de Bierge is a fantastic spot for a good swim. Salto de Bierge is only 7 meters high but is 40 meters wide. Unfortunately it is a manmade dam/waterfall, but nevertheless nice to see.
From Huesca drive east over road A-22 to Perartilla and then take road A-1231 to Bierge (you can make a shortcut). There is a parking near the waterfall Salto de Bierge. Salto de Bierge is a popular spot for a picnic and swimming.