Aquis Querquennis is the ruins of a Roman military camp sit along a flooded section of a river. The construction of the barracks dates back to the reign of Vespasian, around the year 75, when it was likely used as a base from which to defend newly built roads connecting other, larger roads in this remote province.
The walls, arches and moat that form the foundations of this former Roman military camp can sometimes be found half submerged in the reservoir, depending on the amount of rain upriver and the status of the dam.
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.