St John the Baptist Church was probably built in the 1180s as the first rector was installed in 1189. It was refurbished by Jasper Tudor, Duke of Bedford in 1485–95 and again in 1825–27 by the rector Rev. Robert Knight who added the vestry and altered the stone pulpit. The building was restored by John Prichard and John Pollard Seddon in 1860–61 and an organ chamber was added in 1885. More restoration work in 1903 and 1927 included reflooring the nave, reroofing the porch and installing oak stalls in the chancel. A meeting room and vestry wing were added in 1993.
The plan of the building is a tower in the west, nave, south porch, chancel, north-eastern chapel and northern wing. The church is built of roughly coursed grey rubble with grey or yellow ashlar dressings and has a slate roof with stone apex finials. The large and defensive west tower has wide-angle buttresses at each corner and a saddleback roof with embattled and corbelled parapets only on the northern and southern sides. The stone-tiled coping is topped by a weathervane. The northern and southern faces of the tower have four storeys of small round or square openings, although one on the south face is trefoil headed. The eastern facade has large shouldered openings above a corbel table that probably supported a wooden platform. The western side of the tower has a face corbel, reputedly of Saint John the Baptist, above a louvred gable opening, a clock and a three-light window above the ornate western doorway.
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.