The Amphitheatrum Castrense is a Roman amphitheatre next to the church of Santa Croce in Gerusalemme. It is dated to the first decades of the 3rd century AD. It was part of an Imperial villa complex which was built by emperors of the Severan dynasty. The open arches of the outer walls were walled up when the building was incorporated into the Aurelian Walls (271-275 AD), at which point it stopped being used for spectacles and began to be used as fortification, and the ground level around the building was lowered.
In the middle of the 16th century the remains of the second story were demolished for defensive needs. In the 18th century, a Hypogeum was found beneath the arena, filled with the bones of large animals. This leads researchers to believe that the spectacles here included Venationes, the hunting and killing of wild animals. Palladio and Étienne Dupérac made drawings about the ruins.
The building is a regular ellipse 88 meters long and 75.80 meters wide. It is constructed out of brick-faced concrete, with a few decorative elements in travertine. The structure was three stories high but only a section of the lowest story is preserved.
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.