It is a Romanesque castle and monastery located in the province of Huesca in the autonomous region of Aragon, Spain, and is one of the oldest castles in Spain. It was mainly built during the 11th and 12th centuries, when its strategic location at the border of Christian and Muslim lands gave it importance. Construction began around 1020, when Saint Joe Mayor reconquered the surrounding area from Muslim hands. Renowned for its outstanding Romanesque architecture, primarily constructed with limestone, showcasing the architectural techniques and style of the time. The thick walls and sturdy tower showcase the perfect combination of defensive function and aesthetics. It is a representative of medieval structures.