These are a series of photos taken by “urban explorer” Sneakylawyer. He and his girlfriend came across an abandoned hospital in Belgium, displaying the message “There’s beauty in destruction,” which sounds like a line that could have come from the Jokers mouth. Instead of doing the non-cliche ‘walking away’ thing, they decided to enter the scary, dark, derelict building, and came face to face with the Joker himself, albeit in 2D form.
The villainous murals were all created by a person who tags themselves as Pete, or Peteone. I guess we could presume that that is his actual name, but this guy obviously likes Batman, so Pete could easily be his secret identity.
The Joker wasn’t the only thing spray painted on the walls, there was also Batman, Bane, and a group of characters from Batman the Animated Series. My favorite piece, even though partly obstructed, is the Joker with bats swarming in front of his vision. It is a replica of the design created by Jock of DC for the Detective Comics Series.
See below for more examples of the Graffiti.