a second question... google images are hard to find? which U.U. congregation
has the nicest / most opulent / impressive building? i am guessing it is one of the larger ones like all souls in new york or tulsa?
Hmm. There's virtually no UU building that's like an Episcopal or Catholic one, we have no "cathedral" to speak of. The most "opulent" in terms of traditional stained glass and ornamentation that I've seen is the Universalist chapel at Tufts, if that counts. All Souls NYC is like any of the older brick New England churches, but larger; actually very plain inside (as is All Souls in DC, now that I think of it). Most older UU buildings are from the Puritan era, where they didn't believe in stained glass or opulence, but they have a great gravitas of their own just from the woodwork. They felt that fancy trimmings were a distraction from spirituality. I haven't been to All Souls in Tulsa, but from their videos (which you should look up online, BTW, if you're looking for humanist sermons) it looks like it follows the "plain puritan" interior model.
A cool traditional one is King's Chapel in Boston, and within a reasonable walk on the Freedom Trail is the Arlington Street Church (which is kind of Victorian), and First and Second Churches a few blocks away is a contemporary building. If the UUs were going to have a cathedral, it would have been in Boston; but instead they followed their "let's split up into smaller groups!" impulse. The Boston Common and Public Garden is, to me, the Vatican City of our movement, and the Freedom Trail is our Via Dolorosa.
The modern ones are the most impressive to me. The River Road church in Maryland has a beautiful wall of clear glass looking out onto a forest, and a huge vaulted ceiling. I really liked that. The UU church in Deerfield, IL is a modern one with a sculpted interior, stained glass images of science and astronomy, and a huge boulder with a skylight over it as a pulpit. The UU church in San Diego is probably the biggest urban "campus" of the modern churches, though the sanctuary itself isn't huge. There's a huge open courtyard with several buildings around it. Hey, it's Southern California, why stay inside?
The most famous UU buildings are the ones built by or inspired by Frank Lloyd Wright, who was a Unitarian of sorts. Oak Park Illinois has been struggling with maintaining their sanctuary, which is considered the best of his work. There are probably lots of pictures online of that.