Albarracín's crag-top castle was founded in the 9th century. Apart from its perimeter wall and towers, everything you see, including the remains of the Banu Razin rulers' residence, has been excavated in recent years from what had become animal pasture. Visits are by hour-long Spanish-language tours starting at the Museo de Albarracín.
The Fundación Santa María de Albarracín has schedules.