The Milan amphitheatre was built near the Porta Ticinese in the 2nd-3rd centuries AD when Mediolanum grew as economical and political importance while Rome declined. It remained in use until the city was one of the capitals of the Western Roman Empire (4th or 5th centuries). Later it was abandoned after Christianity imposed an end to arena games, but also as, in the wake of the imperial crisis, animals to be used in the amphitheatre were no longer imported. It became a quarry for construction stones as early as the 4th century AD, when the Basilica of San Lorenzo was built.
The edifice was demolished during a Barbarian attack on Milan, as it was located outside the walls and could therefore be used as stronghold by the attackers. The date of the event is uncertain, however: it could be 402, during the Visigothic invasion of Italy, or in 452, when northern Italy was ravaged by Attila, or during the Gothic Wars (6th century).
The scanty remains of the amphitheatre have, however, allowed the archaeologists to calculate that it was 129.5 metres long and 109.3 metres wide.
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.