That is a striking piece of art. Who ever did that was not a splash and dash graffiti artist, but someone who took considerable time. Days possibly, to complete this. Is this in a beer garden, a back yard, or just along the canal?
Above the canal is a broad embankment with walking and bike trails, restaurants, bars and cafes. The entire area seems to be a free area for artists as art, graffiti and tags are abundant. This particular spot is between restaurants but appears to be claimed by one of them for storage. You can get a slightly better idea of the area's colorful configuration at this old post: http://marthasvienna.blogspot.co.at/2009/11/along-donaukanal.html
Love it. That´s not the Vienna that everybody knows.