San Julián de los Prados, often called Santullano, is the pre-Romanesque church in Oviedo that rewards people who go beyond the better-known monuments on Monte Naranco. Built in the reign of Alfonso II in the early 9th century, it is part of the UNESCO-listed monuments of Oviedo and the Kingdom of Asturias.
The outside is plain in the best Asturian way, but the interior is the reason to come: walls covered with geometric and architectural mural painting from the early Middle Ages, astonishingly intact for something this old. Check visiting hours before setting out, as access is more limited than for a normal parish church.