Some of these pieces are incredible.I'm really fond of this one: http://i.imgur.com/sz2ceh.jpg
That said, I've always had a fascination for post-industrial wastelands. The new super-chic hiline in Manhattan for example, used to be a major tagging scene and an amazing space to walk around. You had to find a hole in the barbed wire and climb up but once up there, it was real cool. A more dangerous place was the exposed rails on the west side going under the (manmade) RIverside Park. Lore has it people actually live down there. My buddy (from grad school) and I just peeked in that one. It was almost like something out of a Western: we are walking on the tracks and there is a stretch and we see two figures approaching from the other end: draw? run? (We ran :))