Answer: amphitheater

AnswerCrossword Clue
AMPHITHEATERHollywood Bowl, e.g.
amphitheaterA large circular hollow in rocks or hills
amphitheater(esp. in Greek and Roman architecture) A circular or oval building, typically unroofed, with a central space for the presentation of dramatic or sporting events. Tiers of seats for spectators surround the central space
amphitheaterA sloping, semicircular seating gallery