The Church of San Pedro El Viejo, is located in the old town. In its origins, according to archaeological sources, was Roman temple; Visigoth later, then finally Mozarabic and Romanesque. According to the Bull of Pope Paschal II, 25-May-1107. "The old church of San Pedro with its cemetery, was the only one that had survived in the city of Huesca, and has been used by Christians during the Muslim domination."

The cloister, lies to the south side of the church; retaining its edge in the southeast chapel of St. Bartholomew; Mozarabic single vestige of the temple, now acting as Royal Pantheon.