The church stands in the Boides valley (Villaviciosa), the place where Alfonso III of Asturias was detained when he was dispossessed by his sons, and where there used to be an old convent governed by the Benedictine Order, substituted in the 13th century by the Cistercians.

The church stands on a classic basilica ground plan with a triple sanctuary, separating the central nave from the side aisles with four semicircular arches.

At the western end, there are three enclosures, the central one used as an access vestibule, and two located on the left and right which may have been used to house pilgrims.

The vault over the central nave, like the one over the apses, is barreled with a brick ceiling and decorated with al fresco wall painting, alternating a variety of geometric designs.

Particular elements of this church include the covered gallery annexed to the southern facade at a later date or Royal Portico, the 50 cm square columns on the central naves arches, the triple-arched window open in the central apse, and the room above it, exclusively accessed from the exterior by a window which here has two openings, compared with the habitual three.