The former collegiate church of the Benedictine order, today the Catholic parish church, received the relics of Saint Chrysanthus and Daria in 844. Building was begun in the mid-11th century and completed in the 12th century. It is a romanesque, three-nave buttressed basilica without a transept, with west work and long chancel, as well as an important crypt. Restoration work has been carried out from 1876 to 1893 and since 1957. The interior of the church is well worth seeing.
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.