An old Benedictine monastery built in the second half of the 13th century on an earlier one of the 12th century. The church is one of the few and rare Roman examples of 3 naves and transept in good condition (S. Pedro de Rates and Paços de Sousa). Its original chancel, as in Paços de Sousa, was dismantled and enlarged in 1678, during the rebuilding of the monastic premises. It had an entrance gallery that was demolished in the 17th century. An important feature of this monastery is the defensive tower built in the 14th century, which is considered a stately statement of the monastery. The bell tower is behind the military tower. The cover of the naves is in wood, and that of the headboard in stone vaults.