Theater at Epidauros
"Theatre, Epidaurus, built during the last quarter of the fourth century B.C....The harmony of its cavea, the way it 'sits' in the landscape with the semicircle hollowed out of the side of the hill, and the quality of its acoustics make the Epidaurus theatre one of the great architectural achievements of the fourth century. The circular orchestra provides the link with the stage buildings."
Read More about Theater at Epidauros