The current church of San Tirso is a construction that has gone through major alterations throughout its existence; the latest in the twentieth century, which has resulted in the aspect we see today. Founded around the year 812 by King Alfonso II the Chaste, all that is still visible of the primitive pre-Romanesque building is the upper part of the central apse, with a window with three Roman brick arches, capitals, marble columns and base sections taken from a late Roman construction; all framed by an alfiz.
This three-section window is similar to those seen in the churches of San Julián de los Prados, San Pedru Nora and Santa María de Bendones, all of which were built in the ninth century.
Oviedo/Uviéu. Cathedral of San Salvador. Plaza de Alfonso II El Castro.