What is the term for a large outdoor theatre with rising tiers of seats around an open area?

The term for a large outdoor theatre with rising tiers of seats around an open area is amphitheatre. This architectural structure is characterized by its circular or oval shape, which allows for a central performance area, typically used for various public spectacles, including dramas, music performances, and gladiatorial contests. The design facilitates good visibility for the audience from various angles due to the tiered seating.

While a theatre also serves a similar purpose, it typically refers to a structure that may not be open-air and can be rectangular in shape. The term circus refers to a venue primarily used for chariot races and other spectacles, while coliseum usually refers to specific large amphitheatres, such as the famous Colosseum in Rome. These distinctions clarify why the appropriate term for the described structure is indeed amphitheatre.