Belgian artist Strook (a.k.a. Stefaan De Croock) has created a very interesting mural right outside the STUK art center in Leuven, Belgium. This wall, which was covered in moss, was given a modern makeover by Strook who took a pressure washer and made a relief mural out of it. By blasting away slowly and carefully at the wall, little by little an artwork came into being. What's most impressive is the fact that Strook had never used a pressure washer before and that it was a complete improvisation, with no reference sketch!
Doesn't this remind you of reverse graffiti?