During the archaeological supervision of the construction works of the new shed of the Basel Rowing Club in Kaiseraugst, a hitherto completely unknown amphitheater was discovered last December. The monument will be preserved in the ground. It is the second amphitheater in the canton of Aargau and the third in the Roman city of Augusta Raurica.
The ancient Augusta Raurica, as we already explained in our Augusta Raurica article, the best preserved Roman city north of the Alps gave rise to two modern towns, Augst (the city proper) and Kaiseraugst (the old defensive fort).
As the shed construction project was tangential to a Roman quarry, walls were not expected. That's why archaeologists from the Aargau Cantonal Archeology excavation team were surprised when an oval ring of walls came to light.
The function of the oval ring of walls was not clear at first, and only in the course of excavation was the theory confirmed:it was a Roman amphitheater. The complex is about 50 meters long and 40 meters wide and is situated in the hollow of a quarry abandoned in Roman times, just west of the Kaiseraugst hill fort, the Castrum Rauracense .
In the south of the complex a large gate was discovered, flanked on both sides by two side entrances. The sandstone ashlar threshold has been preserved from the entrance on the west side. On that side of the complex was another entrance to the arena, again with a large sandstone threshold. The inside of the arena wall was plastered. The stands consisted of a wooden construction, from which the imprint of a wooden post could still be traced.
All the signs together, the oval, the entrances and the pole for a tribune, speak in favor of the interpretation as an amphitheater. Based on the building materials used, the finds and the fact that it was built in the abandoned quarry, it dates to Late Antiquity, probably the 4th century AD. This makes it the latest known amphitheater in the Roman Empire.
The monument thus underlines the importance of the Castrum Rauracense in the 4th century AD The castro was an important settlement with a military function on the Roman border, but also an administrative center. At the archaeological site of the imperial city of Augusta Raurica and the Castrum Rauracense they form a single unit. Currently, the site is located in the territory of Aargau and Basel-Landschaft.
The Kaiseraugst amphitheater is the second largest amphitheater in the canton of Aargau after the one in Vindonissa (Windisch). In the Roman city of Augusta Raurica, it is the third monument of this type.
Eight such structures are currently known throughout Switzerland. In addition to Vindonissa and Augusta Raurica, there are amphitheaters in Avenches (Aventicum ), Martigny (Forum Claudii Vallensium ), Nyon (Iulia Equestris Colony ) and on the Enge peninsula in Bern (Brenodurum ). In Roman times, the arenas were used for games such as gladiator fights and animal races, which were very popular at the time.
Thanks to the close and good cooperation with the owner of the building, the construction project could be adapted in such a way that the Kaiseraugst amphitheater will remain on the ground, protected by an embankment. The new building will be built on top. In this way, the monument remains in its original place and is optimally protected so that it is preserved for the future.