SL is so large, in the virtual geographic sense, that one can't keep track of everything; I end up looking for mention of interesting places in blogs, or invitations from friends.
(Does SL have a Rick Steves? Perhaps Vaughn Hannon of Living with the me...)
Lately, New World Notes has been putting up periodic lists of "most popular sims" as determined by where people who use Koinup are visiting (and posting photos from, presumably) the most. I've been going to those places, and they're proving quite beautiful.
Drowsy is a curious, slightly askew place, gently glowing by night. It's a place that is built to look old and worn, and I hope someone writes up its imaginary history--I'd pay to read that. Be sure to explore the woods next to the village and shops.
Empress and Hierophant (that's one sim, not two) is all hills and winding roads, and lots of sheep, some apparently with dreams of being a circus act! It too has gently aged buildings, and the sun shining down through the decaying roof of one feels almost like a cathedral.