Religious, Romanesque and Gothic architecture. Benedictine monastery composed of a church and a rural area on the left side, which extends through the yard, where the entrance is located. Founded in the 9th century, according to the opinion of some researchers, or at the end of the 10th century (985), according to records from that time, it would have been a basilica dedicated to Saint Peter (Monasterio Sancti Petri de Ceti), occupied by Benedictine monks. At the end of the 11th century, the monastery was rebuilt by order of Gonçalo Oveques. At the end of the 13th century and the beginning of the 14th century the church underwent a major remodeling, including changes in the nave's size, reconstruction of the chancel and alteration of the building's facade. The current cloister, the tower and other elements of the complex are the result of the restoration work carried out in the 15th century. The monastery was occupied by members of the Order of São Bento until the 16th century, when D. João III transferred the ownership of the building to the Royal College of Graça de Coimbra (Gracianos).