The castle of San Esteban de Gormaz is one of the key castles that changed ruler once and again during the 10th and 11th century when it finally came under Christian domain. During the reign of King García I, king of Leon, it was reinforced giving place to a repopulation of the town. From there, soldiers would control transit through the Douro River and they would guard the bridge that passed over this river. Nowadays, what is left of the castle is a large wall that is about two metres thick. The castle was built with ashlar stonework, possibly of Roman origin.
Near the access gate, there is a great opening in the ground known as Pozo Lairón, although is not certain what it was used for. The castle is narrow and elongated, and inside there are remains of water pools and underground constructions. Although it is quite deteriorated, it is of great importance due to its strategical location from which you can see the castle of Gormaz.
References:Sigmaringen Castle was first mentioned in the year 1077 in the chronicles of Petershausen monastery. The oldest parts of the castle are concealed beneath the alterations made during the 17th and the 19th centuries. The secret of the earliest settlement built on this defendable rock will never be fully revealed: large-scale excavation work would be necessary, which the extensive land development renders impossible. Judging from the many Roman remains unearthed in the area around Sigmaringen, the 12th century keep known as the 'Roman Tower' could be traced back to a Roman predecessor.
The castle remains that have been preserved (gate, great hall and keep) date back to the Staufer period around 1200. The castle remains were integrated into subsequent buildings. The foundations of the castle buildings are to a large extent identical to the surrounding castle wall.
These remains give us a good idea of how the castle might have looked during the 12th century.