Not surprisingly, Rome had a great presence in Switzerland. I am, however, surprised that this is the eighth Roman amphitheater found in that country.
“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.”
“Augusta Raurica, or Colonia Augusta Rauracorum, was founded by Lucius Munatius Plancus around 44 BC in the vicinity of a local Gallic tribe, the Rauraci. During the 2nd century AD, the town emerged as a prosperous commercial trading centre with an estimated population of around 20,000 inhabitants.
The amphitheatre was uncovered during the construction of a new boathouse for the Basel Rowing Club on the Rhine in Kaiseraugst, revealing an oval ring of walls that measure around 50 metres long and 40 metres wide, west of the Kaiseraugst fort, the Castrum Rauracense.”
https://www.heritagedaily.com/2022/01/roman-amphitheatre-unearthed-in-switzerland/142560?amp
https://www.thearchaeologist.org/blog/swiss-archeologists-dig-up-youngest-roman-amphitheatre-in-kaiseraugst?format=amp