An amphitheatre (or amphitheater) is an open-air venue used for entertainment and performances. The term derives from the ancient Greek ἀμφιθέατρον (amphitheatron), from ἀμφί (amphi), meaning "on both sides" or "around" and θέατρον (théātron), meaning "place for viewing".
Ancient Greek theatres were built to a semicircular plan, with tiered seating above a performance area. Ancient Roman amphitheatres were oval or circular in plan, with seating tiers that surrounded the central performance area, like a modern open-air stadium. Modern usage for "amphitheater" can embrace theatre-style stages with the audience only on one side, theatres in the round, and stadiums. Natural formations shaped like man-made theatres or amphitheatres are sometimes known as natural amphitheatres.
Read more about Amphitheatre: Roman Amphitheatres, Contemporary Amphitheatres, Natural Amphitheatres