That which resembles a theater in form, use, or the like; a place rising by steps or gradations, like the seats of a theater.
In ancient Greece and Rome, an open-air structure in the form of a segment of a circle, frequently excavated from a hillside, with the seats arranged in tiers behind and above one another.
Parts of a classical theater in Roman times include: the cavea, or seating area; an orchestra, the semicircular area between the cavea and the stage; and the scenae frons, or stage backdrop. Horizontal aisles called diazomata divided the cavea into upper and lower sections. The audience entered and exited through parodoi, vaulted passageways leading to the orchestra floor on either side of the stage. Smaller tunnels, called vomitoria, debouched on the upper rows of seats. The scenae frons was a brick construction, two or three stories high, with three doors at stage level through which the actors made their entrances and exits. It was furnished with statuary niches, and brightly decorated in colored stone, marble, and plaster.