San Giovanni a Porta Latina (Italian: 'Saint John Before the Latin Gate') is a Basilica church near the Aurelian Wall. According to Tertullian, in year 92, St John the Evangelist survived martyrdom at Rome under the Emperor Domitian by being immersed in a vat of boiling oil, from which he emerged unharmed. He was later exiled to island of Patmos. This event was traditionally said to have occurred at the Latin Gate (located on the southern portion of the Roman wall). The nearby chapel of San Giovanni in Oleo is said to be on this very spot. The event was referred to in the Roman Martyrology, which was begun in the seventh century, when already there was a celebration of the event.
The tradition for the building of the Basilica of St. John at the Latin Gate places its construction during the pontificate of Pope Gelasius I (492-496). This is consistent with the oldest of the roof tiles, which have the imprint of a taxation stamp for the Ostrogoth King and ruler of Italy Theodoric the Great (reigned 493-526). One of these ancient roof tiles is now used in the Basilica as a lectern.
In the 8th century, the Basilica was restored by Pope Adrian I, and later the bell-tower and portico were added, and at the end of the 12th century the Basilica was reconsecrated by Pope Celestine III. In the 16th and 17th centuries, a Baroque ceiling and other Baroque features were added to the interior. In the years 1940-1941, the Baroque features were removed and the Basilica was returned to a more primitive simplicity. This last renovation was carried out by the Rosminian Fathers, who, in 1938, were given care of the Basilica and the nearby building, where they opened the Collegio Missionario Antonio Rosmini which houses their International House of Studies.
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.