I went to Rome and Israel with a group of 30 people from my parish in November. I was chosen as the "designated singer" for the trip, and the tour guides often asked me to sing something to demonstrate the acoustics of one church or another that we visited. Can't say I came across any particularly wonderful acoustics in Rome, but there were lots of small chapels in Israel that were absolutely wonderful for singing. I got all 30 people singing their hearts out in a few of those places, and it was a real pleasure. If the acoustics are good, it's a lot easier to get a group to sing with confidence.
I was about to try singing in the Roman amphitheater in Caesarea in Israel, but we were invaded at that moment by three busloads of school kids. Spoiled the ambience, but I was glad they got a chance to see that ancient, beautiful spot by the Mediterranean.
-Joe Offer-