The Basilica of Saints John and Paul on the Caelian Hill was built in 398 AD over the home of two Roman soldiers, John and Paul, martyred under the emperor Julian in 362. The church was thus called the Titulus Pammachii and is recorded as such in the acts of the synod held by Pope Symmachus in 499.
The church was damaged during the sack by Alaric I (410) and because of an earthquake (442), restored by Pope Paschal I (824), sacked again by the Normans (1084), and again restored, with the addition of a monastery and a bell tower.
The church has three naves, with pillars joined to the original columns. The altar is built over a bath, which holds the remains of the two martyrs. The apse is frescoed with Christ in Glory (1588) by Cristoforo Roncalli. Below this fresco are three paintings: a Martyrdom of St John, a Martyrdom of St Paul, and the Conversion of Terenziano (1726) by Giovanni Domenico Piastrini, Giacomo Triga, and Pietro Andrea Barbieri.
During excavations performed in the 19th century, a series of Ancient Roman rooms were discovered under the nave of the church. Some of these rooms date back to the first and fourth centuries AD. In one room an elegant third-century AD fresco depicting Proserpine and other divinities among cherubs in a boat can be found, as can traces of another marine fresco and mosaics in the window arches.
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.