The theatre was built in the 1st century BC during the reign of Emperor Augustus, and is one of the oldest in Gaul. East-facing, it was built on the side of Fourvière hill which overlooks the city. This type of structure is called an amphitheatre. An amphitheatre is a circular, semicircular or curved, performance space, usually located outdoors. Emperor Hadrian expanded the theatre in the 2nd century by building additional seating further up the hill. At this time, the building could therefore have seated an audience of up to 10,000.