The Church of St John the Baptist was founded by William FitzOsbern and given to an abbey in Normandy. The nave may be 11th century, as may be the Norman font. A north aisle was added at the end of the 12th century and a south aisle shortly afterwards. In the 14th century the chancel was rebuilt and the south porch was added. In the 15th century a chapel was added south of the chancel and east of the south aisle, and a four-centred arch was inserted in the south wall of the chancel to link it with the chapel. The north aisle was demolished, its arcade filled in and two-light Perpendicular Gothic windows inserted in each of the filled-in arches. The Perpendicular Gothic west tower was added towards the end of the 15th century. The square-headed windows in the south aisle were inserted in the 16th century and the spire was added to the tower probably early in the 17th century.
On the wall can be found a memorial portrait by John Flaxman, showing a woman holding pelicans in her hand in relief. The chancel has a modern reredos.
In front of the porch is a 19th-century Celtic cross by Joseph Clarke on the four steps of the old churchyard cross.
Near the Celtic cross a marble monument marks the grave of Edward Edwards, (1812–1886) the pioneer of the public library movement. The churchyard also contains four Commonwealth war graves of service personnel, three from World War I and one from World War II.
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.