The Santuário do Senhor da Pedra is the unusual six-sided sanctuary on the southern edge of town, visible from the road as you arrive. Designed in the 1740s by Rodrigo Franco, it has a sinuous Baroque facade and a striking hexagonal nave — a piece of 18th-century church architecture out of character with the medieval town behind it.
Entry is free but the church is open only at limited times. Even from the outside the building is worth a slow look as you pass on the way to the walls.