The Porta Asinaria is a gate in the Aurelian Walls of Rome. Dominated by two protruding tower blocks and associated guard rooms, it was built between 270 and 273, at the same time as the Wall itself. It is through this gate that East Roman troops under General Belisarius entered the city in 536, reclaiming the city for the Byzantine Empire from the Ostrogoths.
By the 16th century it had become overwhelmed by traffic. A new breach in the walls was made nearby to create the Porta San Giovanni. At this point, the Porta Asinaria was closed to traffic.
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.