Here in California we have many Missions with great accoustics, but the one I deal with most is the San Luis Rey Mission in Oceanside, Ca. The main body of the sanctuaries walls are totally covered in plaster and the floor is paved in glazed brick. Over the intersection of the cross is a tall dome. To stand under the dome is an (a religious) experience. Also attached to the main body of the sanctuary is a small domed chapel. To sing in there accapella is to die for. I advise anyone who comes to visit the mission to try it. You will possitively cry with joy.