Castillo de Almonacid de la Sierra, located in Zaragoza's Aragon region, is a fortress with roots extending back to the 11th-century Muslim period. Also known as the Castle of los Luna or Al-Monastir, the medieval structure was rebuilt during the 14th-15th centuries and features a rectangular enclosure measuring 40 by 25 meters with six rectangular towers. Now privately owned and serving as a residence, the castle has undergone partial restoration while remaining in progressive ruin. Protected under Spanish heritage law since 1949, the fortress represents an important example of medieval fortification that blends Muslim and Christian architectural periods.
