From our river ship I got to cycle one day and was overwhelmed with the grafiti or "wall art" on any blank space. I have since heard that some areas are rented or bought in order to express yourself with paint. Great opportunity if you live in Europe--open a spray paint store!
Some so called art even appears to be from children? Maybe teachers encourage this, who knows?
I spent the morning at the Albertina museum and realized after I took the picture that the risers of the stairs depict Monet's lily pond. Pretty clever.