Saint William's Church is a gothic church is known for its sumptuous interior combining the Gothic and Baroque styles. Since the end of the 19th century, the excellent acoustics of the church has allowed it to serve as a venue for concerts of classical music, in particular for the Passions of Johann Sebastian Bach.
Returning unharmed from the Crusades, the knight Henri de Müllenheim undertook the construction of a monastery for the Hermits of Saint William, an order of mendicant monks, in this marshy neighbourhood situated extra muros, that is, beyond the city walls. The elongated building, consecrated in 1301 and realised in 1307, is the only remnant of this group. Entirely brick and unvaulted, the church corresponds well to the ideal of the order, namely by its single nave and the simplicity of its exterior form. Sheltered by a pitched roof, its nave is topped and prolonged by a deep polygonal choir illuminated by high windows, which betrays its original function as the monks' meeting room. In 1331, by reason of its proximity to the port and wharfs, the church was chosen as parish by the newly established corporation of shipbuilders.
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.