It goes without saying that Spain is an embarrassment of riches-- in terms of history, architecture, and natural beauty, perhaps the richest country on earth, IMHO of course.

On the Basque coast, you might be interested in the prehistoric cave paintings of Altamira, outside of Santillana del Mar. I think the actual caves are now closed to tourists, (something about human respiration upsetting the delicate humidity balance inside the caves,) but I think there is a mock-up, and a museum. In the area of La Rioja and León that you'll be in, I highly recommend El Monasterio de Santo Domingo de Silos. It contains a romanesque cloister said to be the most beautiful in Spain, (and I agree.) Just down the road there is a miniature river gorge ideal for a short hike, Las Yeclas. If I'm not mistaken, the smash CD hit of a few years ago, CHANT, was recorded by the Benedictine monks who still live, work, and chant within the cloistered walls of Silos.

A suggestion I would politely make is that three days in Sto. Domingo de la Calzada might be one day too long. If you're using it as a base for day-trips, it's probably O.K. You shouldn't miss Burgos, if you haven't already been there. Spending a night there might be a nice compromise.

In Haro, I enjoyed touring a few of the wineries since the city is the capital of the Rioja region. I'll think of more later, I'm sure.

Joel