A small, austere Romanesque chapel of granite blocks, sitting on the slope between the castle and the ducal palace. Tradition holds that Afonso Henriques was baptised here as an infant, and there is a stone font inside that is claimed — without much evidence — to be the one used.
The building itself is plain and quiet, with a single nave, a few medieval tombstones set into the floor, and a low arched doorway. Five minutes is enough, but it is exactly the right thing to see between the castle and the palace.