I've only stayed in three Paradors in Spain, but these were in the North while walking the Camino de Santiago - they were a great break from sleeping in pilgrims albergues! None were castles, but all were renovated 15th/16th century buildings.
My favourite was San Marcos, an old monastery in Leon which has the most beautiful, imposing facade. While I stayed in the annex at the back, this had been built and furnished in the style of the original and I could still wander around the entire building, including the cloister, and the library which has a tiny balcony into the adjoining church.
Also stayed at the Parador in Santo Domingo de la Calzada and in Sntiago de Compostela, both were built as pilgrim hospices. Both buildings are lovely, though Santo Domingo was the smallest of the three.
I do suggest you book through the official Parador website, and you can view each Parador before you book: http://www.parador.es/en/portal.do
There are many great Paradores all over Spain and nearly all of them are in historic buildings. I have only stayed in one - the Parador de Tortosa near Valencia.
Just the other side of the border to Biarritz is one the most famous ones - the Parador de Hondarribia though it is also one of the most expensive. Again, I haven't stayed here but I have taken clients so I have seen some of the interior and most of the exterior.
As you don't say exactly where you are going in the NW of Spain use the search function on the Parador website. In the drop down menus on the left the first gives you the option of which Autonomous Community. For the NW you will be looking at (probably); Galicia, Asturias and Castilla León.
The second drop down menu allows you to select Parador's by the type of building.
One of my favourites Parador buildings in all of Spain is the Cardona but it is in the NE of Spain.
I stayed in the Parador in Hondarribia few weeks ago. It was a fascinating place, but if you want another interesting Parador, the 8thcentury castle in Cardona is a Parador. It's about 50 kilometres inland from Barcelona. I have been to both of them.
The best Parador in Spain is in Granada. Inside the gardens and part of Alhambra Arabian Palace.
If you get a room there you'll be one of the few lucky tourists that managed a reservation there.
http://www.paradores-spain.com/spain/pgr...
In and around segovia, theres some amazing castles. Not NW, more W and toward the middle but thats where the good castles are at. Google segovia castle.
Planning a trip in September in the NW of the country, and particularly fond of castles or historic buildings. Any advice?
