When I found this little winding alleyway I was a little hesitant about going down it as I was unsure where it led and there was a lot of graffiti around. But I did walk down it and found that the walls were entirely covered in colourful graffiti that would not be out of place in an art gallery.
The alleyway is called Werregarenstraat and runs between Hoogpoort and Onderstraat. If you are in Hoogpoort find the back entrance to the Novotel hotel and the alleyway is directly opposite. In fact my room overlooked the entrance and that is what made me wonder where it led to.