The construction of a new boathouse for the Basel Rowing Club on the Rhine in Kaiseraugst was accompanied at the beginning of December 2021 by the excavation team of the Aargau Cantonal Archaeology. Since the construction project affected a Roman quarry, walls were not expected. The archaeologists were all the more surprised when an oval ring of walls came to light, as reported by the Aargau cantonal archeology on Wednesday morning.

An amphitheater from late antiquity

The function of the oval ring of walls was initially unclear and only in the course of the excavation did the thesis come true: it is a Roman amphitheater. The facility is around 50 meters long and 40 meters wide and is located in the valley of a quarry that was abandoned in Roman times.

This is immediately west of the Kaiseraugst fort, the Castrum Rauracense. A large gate was uncovered to the south of the complex, which was flanked on both sides by two side entrances. The threshold made of sandstone blocks from the western side entrance was still preserved. On the west side of the complex there was another entrance to the arena, again with a large sandstone threshold. The inside of the arena wall was plastered.

The youngest known amphitheater of the Roman Empire

The grandstands consisted of a wooden construction, from which the imprint of a wooden post could still be proven. All the evidence together, the oval, the entrances and the placement of the posts for a grandstand, speak for an amphitheater. Due to the building materials used, the finds and the fact that it was built in an abandoned quarry, it dates to late antiquity, probably to the 4th century AD.

This makes it the youngest known amphitheater in the Roman Empire. The monument thus underlines the importance of the Castrum Rauracense in the 4th century AD.

The fort was an important settlement with a military function on the Roman border, but also an administrative center. The Roman city of Augusta Raurica, the archaeological site of the Roman city of Augusta Raurica and the late antique Castrum Rauracense, form a unit. Today the site extends to both the Aargau and the Basel area.

The second amphitheater next to Vindonissa in Aargau - the eighth in Switzerland

The Kaiseraugst amphitheater is the second amphitheater in the canton of Aargau after the one in Vindonissa (Windisch). It is the third such monument in the Roman town of Augusta Raurica. Eight such buildings are now known throughout Switzerland.

In addition to Vindonissa and Augusta Raurica, there is an amphitheater in Avenches (Aventicum), Martigny (Forum Claudii Vallensium), Nyon (Colonia Iulia Equestris) and on the Enge peninsula in Bern (Brenodurum). In Roman times, games such as gladiator fights and animal hunts were presented in the arenas, which were very popular at the time.

Thanks to the close and good cooperation with the client, the construction project could be adapted in such a way that the Kaiseraugst amphitheater was preserved in the ground. The archaeological substance is protected by a dam. The new building will be erected above it. The monument thus remains in its original place and is optimally protected so that it will be preserved for the future.