Istein castle was a rock castle built by the bishops of Basel in the 11th and 12th centuries. It was first time mentioned in 1185. The castle was stormed in 1410-1411 by the Basler troops. The modern fortress was built in 1900-1914 and destroyed after 1945.
St. Vitus Chapel, partially ruined, is one of two original castle chapels built in the 12th centurya. The current small chapel, which was built after the destruction of the castle in 1650 and destroyed by the French occupation forces in 1947, was rebuilt in the 1980s due to a citizens' initiative.
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.