It is amazing how just empty abandoned places calling people to do something with this blank spaces. There are some really good Artists who can work with graffiti and the Artworks of them are huge sizes and sometimes so complex. I love to visit such areas and I know in our area some buildings even asked such Artists to make an artwork on their white wall so that it is not spoiled by hooligans. Once it is done and signed by those guys nobody even try to do anything and destroy such Artwork. That is a kind of rule of the free street Artists :)