I can't explain why, but this was my favorite sight in Barcelona! Originally we weren't even going to go here because we were just wandering around on our second (and last) day here, but we happened to wind up there and I'm so glad we did. It was truly breathtaking. We ended up sitting on a bench in front of it for a good half hour just looking at it, appreciating where we were.
There's also plenty of people watching opportunities as you see people trying to take selfies with the Cathedral.