Tvis Abbey is a former Cistercian abbey founded in 1163 by Prince Buris as a daughter house of Herrevad Abbey in Scania (now in Sweden). The abbey was dissolved during the Reformation, probably in 1547. The abbey church, which served as a parish church, was demolished, apparently in 1698, after which a replacement was set up in the west wing, but that too was demolished after the construction of a new parish church in 1887. Today there are no visible remains apart from the foundations.
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.