This I found a sight to go really out of your way for. You have to anyway because it's quite a long drive from the major motorway between Lisbon and Porto.

On the outside the complex looks like a massive, fortress-like castle. When you go inside (through a tiny and well-hidden door) the richnesses of the convent come to you.

The major attraction inside, in the church, is the charola, a Romanesque rotunda full of frescoes and gold.