The Monastery of Santa María served for centuries as the organizational centre for the agriculture and economy of this area of western Asturias. It was founded in 1137 by King Alfonso VII and his wife Berengaria as a monastery of Benedictine monks, but was later occupied by the Cistercian Order.
All its assets became civil property after the Ecclesiastical Confiscations of Mendizábal, except for the church, which became the parish church. The monastic buildings were sold and converted into private homes, except for the cloister, which is in ruins.
Of the original Romanesque construction, only the church remains, with the typical 12th-century monastic layout: three naves with the central one standing higher than the other two, covered with a wooden ceiling, and a triple apse, with barrel vaulting and cul-de-four. The interior is noteworthy for its simplicity and decorative austerity. The naves, distributed in five sections, are separated by pointed arches which are supported by cross-shaped pillars. The only outstanding decorative motif is the tomb of Juan Álvarez Osorio, located in the presbytery, which is protected by an arcosolium, corbels and cornice decorated with symbolic funerary references.
The most recent building is the monastery, dating from the 17th and 18th centuries, the construction of which is attributed to the master builder of the cathedral of Santiago de Compostela, Domingo Lois Monteagudo. Adjoining the south side of the church, the building is of grandiose proportions built in a severe and austere architectural style. The entrance comprises a beautiful portal, formed by an original arch with outstanding voussoirs between two pilasters that are prolonged on the cornice. A balcony with no railing juts out above the doorway, surrounded by the coats of arms of Spain and the Cistercian Order. The entire façade is made of slate ashlar and the roof, slate shingles, the predominant material in western Asturias.
