Los Angeles: Bradbury Building
I don't have a huge knowledge of architectural design, but I can appreciate a beautiful structure when I see it. Or don't see it.
Because actually, the thing about the Bradbury Building that makes it so unique and special is the inside.
Built in 1893 (over 100 years ago!), the Bradbury Building in downtown Los Angeles has the most beautiful wrought-iron work going all the way up to the fifth floor to the skylight at the top. The oak railings and wood engravings with the iron work offer a beautiful juxtaposition of natural and industrial, with a combined elegance of detail.
It doesn't take long to appreciate it — there are actual people living and working in the building, so you're only allowed in on the first floor and can walk up the first staircase (which is slightly disappointing because you see how cool the elevator is and just want to take a ride inside).
The building has become popular for people that recognize it in movies like Blade Runner and (500) Days of Summer. I'm jealous of these guys that did get to ride the elevator, and features clips from familiar movies.
Additionally, there's this awesome theater across the street. I've never been inside, but the outside is my favorite thing.