I am looking for specific structures or formations with great acousitics.?

I want specific places with great acoustics. I do know of the Mayan arena and a couple of whisper rooms. I also know that there are natural places where people like to play music because of accoustic do to rock formations, or buildings that are built in such a way to take advantage of acoustics. That is more what I want. I don't want theaters, unless they are unique. Also, I'm asking this question again, because my last one was deleted and no one will tell me why. So, please, no profanity, spam, etc. I really want to know the answer to this.