A sober and elegant church which used to be a parish and collegiate church, and today functions as a pro-cathedral to the newly re-founded Barbastro-Monzón diocese.
It was built in the 12th-13th centuries on the first Christian church in town, consecrated in 1095, shortly after the Reconquest. It is, therefore, a chiefly Romanesque church, although it has been remodelled several times since the 15th century. The floor plan consists of three naves, transept and triple apse, above which we mainly find barrel vaults, or slightly pointed arches, typical of the time. It appears large and sober, probably influenced by the Cistercian spirit emanating from the adjoining convent-castle of the Monzón Knights Templar. It was refurbished several times over the centuries: the Baroque-Mudejar tower was built in the 17th century, rising up over the transept resting on the old lantern of the church's original dome, with Gothic cross vaults.