The Nus castle stands above the same name village on a rocky projection, which dominates the entrance to the valley of Saint-Barthélemy. According to available documentation, the building can be traced at least as far back as the end of the 13th century, although the quadrangular turret, which collapsed at the start of the 20th century, and which stood in the eastern sector of the castle, can be compared to the towers erected in the valley during the 11th and 12th centuries. The final layout of the castle, which was modified on several occasions during the 14th and 15the centuries, was the product of a radical reconstruction campaign which took place around 1595, the date inscribed on the architrave at the entrance to the courtyard.
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.