Located in the borough of Pravia, only a few traces remain in the nave and side walls of the original basilica built in 780. It consisted of three naves with a transept and three rectangular chapels. Above the transept arch there used to be an intricate inscription formed by the words Silo Princeps Fecit. A vestibule served as the Royal Pantheon. The arches were semi-circular on square pilasters and the ceiling was wooden.
The main altar is a replica of the original, which since 1984 is located in the crypt of the Church of Jesus of Nazareth, in El Pito (Cudillero).
The bell gable, built in 1868, which stood at the west end and did not correspond to the original building, was attached to the south sacristy in the last restoration carried out by Luis Menéndez-Pidal y Álvarez between 1979 and 1980.
The Pre-Romanesque remains it conserves include parts of columns of the triumphal arch, two small horseshoe-arch windows, a mullioned window and several catalogued remains located in the sacristy.
It boasts an interesting Romanesque Calvary in the south transept.
