The amphitheater at Epidaurus was constructed in the 5th century BC, seats 14,000 people, and is intact. It's still used for theater productions in the summer. The acoustics at Epidaurus are very nearly perfect. A person standing at the center of the stage can speak in a whisper and be heard perfectly by someone all the way up in the nosebleed seats. I stood at the center of the stage and felt a strange phenomenon as I spoke: the sound of my voice reverberated back to me in such a strong echo, I could feel its pressure against my face. It was like talking with my head inside a steel drum. It did not feel like I was outdoors at all.