Berlin is maybe one of the coolest, but not necessarily the most beautiful city in the world. Well, at least not at first sight. But if you get to know it a little bit you might find some of its hidden beauty. For American photographer Marc Gruninger it must have been an experience like that. With his photo series Hinterhof he captured a hidden side of Berlin that many of those living here or visiting might never have noticed before. But all you have to do is step into the backyard of your house and look up and you might also find one of these stunning framed views of the sky. Enjoy some examples of his unique series after the jump.