A church at the site of Sant'Agata was present by the 8th century, when the neighborhood was located outside the city walls, but after the 1184 fire destroyed the ancient church, it was reconstructed in the 15th-century in Gothic style. Destruction by fire of this church was somewhat paradoxical, since Saint Agatha was the saint invoked for protection against fires. Further modifications were completed along the centuries, leading to a pastiche of styles. The incomplete 14th-century facade has a Renaissance architecture facade, decorated with Baroque statuary.
Inside, the presbytery dates from the 15th century, the ceiling from the 16th century, the altars and fresco decoration from the 1680s, and the chapel of the Santissimo Sacramento is from the 18th century. The main altarpiece depicting Sant'Agata with Saints Peter, Paul, Lucia, Apollonia standing before the cross (1522) is a masterwork by Francesco Prata from Caravaggio.
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.