This was beautiful to listen to. By pure luck (should have done more reading), I was visiting Pisa in Italy. There's a building (the baptistry) _beside_ the leaning tower, which has the most perfect acoustics.

Every hour, they close the doors and a person sings a series of individual notes which then interact just _beautifully_ in the building. Hard to describe. There's a soundcloud[1] here, not mine, stars properly around 1:23. I think you really have to be there though, it was wonderful.

[1] https://soundcloud.com/miguelisazam/pisa-baptistry-of-st-joh... [2] https://en.wikipedia.org/wiki/Pisa_Baptistery