The Castle of Charles V is located in the strategic area of Hondarribia, at its highest point. It still conserves the structure of a medieval fortress and its defensive appearance. It was built in the 10th century by King Sancho Abarca of Navarre, although it was subsequently reformed by Emperor Charles V. The building served as both a castle and a palace, both connected by an interior courtyard. The castle had a square floor plan with sturdy walls. Highlights of the main facade include the doorway, rather small in size and decorated with an arch framed by the characteristic Islamic moulding known as an alfiz, over which can be seen the imperial coat of arms with the two-headed eagle of Charles V. It has today been restored and converted into a Parador hotel.
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.