Leiria's Sé Catedral sits in the heart of the old town, between the castle and the central square. It was begun in 1559 under King Sebastião and finished only in the eighteenth century, which gives it the slightly mismatched look of a building that outlived its original plan.
The interior is unusually plain for a Portuguese cathedral — whitewashed walls, gilded retables only at the high altar, and a sober timber ceiling. Look for the trompe-l'oeil paintings flanking the altar and the carved choir stalls. Entry is free.