The Circus of Maxentius is an ancient part of a complex erected by emperor Maxentius on the Via Appia between AD 306 and 312. It is situated between the second and third miles of the Via Appia between the basilica and catacombs of San Sebastiano and the imposing late republican tomb of Caecilia Metella, which dominates the hill that rises immediately to the east of the complex.
The Circus itself is the best preserved in the area of Rome, and is second only in size to the Circus Maximus in Rome. The only games recorded at the circus were its inaugural ones and these are generally thought to have been funerary in character. They would have been held in honour of Maxentius' son Valerius Romulus, who died in AD 309 at a very young age and who was probably interred in the adjacent cylindrical tomb (tomb of Romulus). The imperial box of the circus is connected, via a covered portico, to the villa of Maxentius, whose scant remains are today obscured by dense foliage, except for the apse of the basilical audience hall, which pokes out from the tree tops. The complex was probably never used after the death of Maxentius in AD 312.
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.