This shot by my Flickr friend tom.wright is a beautifully composed black and white rendition of one of Gaudi's chimneys on the roof of La Pedrera "the Stone Quarry" (also known as Casa Mila). I love how the symmetry suddenly gets broken near the bottom of the shot. As good as this one is, I really urge you to explore the other shots of this location in his stream as well. I did a double take when I saw some of them as they instantaneously reminded me of Star Wars storm troopers - and indeed, it is said that George Lucas got his inspiration from this spot.
All rights retained by the photographer.