Do Not Look At This Ad, Perv
The little white letters in this photo are advertising the 28th Biennale of Graphic Art, in Slovenia. So uh, what's that shape in the background, then? NSFW, is what it is, so do not click through to find out.
Small letters, the largest of which is much smaller than even a nipple, had been used deliberately to force necessarily those interested passers potschatelney examine billboard in search of those responsible for such a bold advertising solution.