At first you see graffiti.
But when you walk to the right spot...
Everything becomes clear.
You just had to see her from a certain angle. (Unfortunately she's the mythical Gorgon monster Medusa, so when you do see her, you're turned to stone.) She was created by the Italian art studio Truly Design.
Medusa, anamorph - Ninja1 and Mach505, Truly Design>>