Atlanta's Episcopal cathedral in Buckhead, a vast 1962 Gothic Revival pile in Indiana limestone. It is the largest Episcopal church in the country by some measures, with a nave that seats over 1,700 and a notable Aeolian-Skinner pipe organ.
The cathedral runs free organ recitals during the week and Sunday evensong is open to visitors. Worth a look on a Buckhead detour; the parish gardens are open during daylight hours.