Roman Theatre (Mainz)
Altstadt, Germany
The Roman Theatre in Mainz, Rhineland Palatinate (ancient Mogontiacum) was excavated in the late 1990s. It is located immediately next to the Mainz Römisches Theater station and was once the largest Roman theatre north of the Alps, with a diameter of 116 metres, a stage-width of 42 metres, and a capacity of roughly ten thousand people.
Venue data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).