Have a look around
As you can see, the village is built on a hill and dominated by the castle. A small stream, which used to be a major river, separates the old town from the new. The castle isn't much preserved, but it's free to enter and you can go anytime. I often go at night; I have it to myself and it's very peaceful. If you've come by bus, you'll have been let off at the mercado. Skip the vegetables (they're expensive and you'll do much better at the Saturday morning farmers' market), but it's a great place for fresh fish.