For years graffiti writers and street artists have sought these undiscovered spots as a kind of refuge, an urban backyard for hanging out and going big, often collaboratively. You could say that rooftop spots even have a certain lore, a place to tell stories about and revel in. In a hard-knock nasty city that sometimes seems to swallow people whole, on a rooftop with a view you can do a huge piece and feel like you are holding it all down.