The rude, dismantled pile of the Castle of San Servando, which crowns the height opposite to the Bridge of Alcantara, marks the site of a monastery, erected by Alfonso VI. in gratitude for his escape from the rout of Sacralias (1086). It was peopled by Benedictines from Sahagun and Cluny. These holy men soon found by the defensive works with which their new home was provided that their duties would not be entirely of a clerical description. Yusuf-ben-Tashfin, the Almoravide leader, almost destroyed the building during his abortive siege of Toledo, and Alfonso subsequently gave the establishment the aspect and features of a fortress. As such it bore the brunt of the repeated Saracen onslaughts in the first half of the twelfth century. It was abandoned in consequence by the monks, and was bestowed by Alfonso VIII. on the Knights Templars. It continued in their possession till the suppression of the Order in 1312. It seems to have fallen into ruins soon after, and was rebuilt about 1386, on the initiative of the great archbishop, Tenorio. It is not a very interesting monument. It is built of masonry, with facings of red brick here and there. Three of its four sides are standing, and the same number of towers. These bear a resemblance to the outer or circular tower of the Puerta del Sol. The windows and arches exhibit Moorish, or rather Mudejar, influence. The castle in its day must have been a fine specimen of the mediæval stronghold. To-day its ruin is complete. It serves as a home to the owl and the bat, and the very ghosts of monks and templars seem to have deserted it as uninhabitable. The castle is referred to by Calderon and other writers, and seems at one time to have been a favourite spot for duels.