Bulwarked Frontier Fortifications by Anonymous WHS Traveller
This is one of the most beautiful places in the world. I have been the last year and it is a unique experience. It combines a fantastic natural landscape with spiritual buildings.
You can visit with a low cost flight from London (or Brussels, Düsseldorf, etc) to Valladolid airport (Villanubla). There, the best way to visit the zone is hiring a car (there are a lot of small villages to see).