What about that Neanderthal cave system the Hypogeum of Hal Saflieni in Malta? The acoustics rdelliberately designed for ritual chanting.

http://www.ancient-origins.net/news-history-archaeology-mysterious-phenomena/experts-unravel-sound-effects-malta-s-hypogeum-hal

I have a CD of a female singer who recorded somgs in this. Can't remember her name though.