Reverse graffiti

I found this through a link in my RSS feeds:


He's creating the skulls by cleaning the pollution from the walls.
I believe the police were taking notes, not ticketing him. I think the end result was the artist's aim - having the local government clean the pollution from the tunnel.

It's a really interesting concepts to me, and I love the comments on YouTube going back and forth about whether it was a shame that the art got cleaned off, or if that was the artist's aim.