Serdica Amphitheatre was part of the ancient Roman city of Ulpia Serdica, now Sofia, the capital of Bulgaria. Discovered in 2004 and the subject of excavations in 2005 and 2006, the ruins of the amphitheatre lie on two adjacent sites in the centre of modern Sofia. The amphitheatre was built in the 3rd–4th century AD on top of a 2nd–3rd century theatre, which had been ravaged by the Goths. However, the amphitheatre remained in use for less than a century and was abandoned by the 5th century.
The Amphitheatre of Serdica was among the biggest in the eastern part of the Roman Empire and the largest in what is today Bulgaria. It lay outside the city walls of Serdica and hosted fights between gladiators and wild beasts, which were advertised at the entrance of the city.
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.