Fly Robin Fly!
.......ummm that's okay, Batman. You just go ahead and replace him like all the others.
All those cities with super-heroes and villains must have signs like this, at least to warn people about pieces concrete getting knocked off during fight scenes and what not raining down on the civilians below. Or maybe the people are just used to it.
That wall-climbing bit was my favourite "special effect", that and the giant hour-glass. More signage
UPDATE - Changed the shape of the sign.