Any travel guide will probably tell you to avoid this particular spot in Berlin. The going joke is "In other parts of the city, you'll find needles or bottles or puke on the steet. If you want to see the full tableau, visit the Kotti". If you do dare to visit, I recommend two things: Tadim Döner, who produce one of the best Kebabs in the city, and, since you are already in the area, that you dare sneak a peak at the backside of the eyesore that is the Zentrum Kreuzberg.
According to the Berlin Streetart Blog(link in German), it is one of the hotspots for creative tagging in the city. I tend to concur.
There you will find many and varied forms of expression, some by street artists documented elsewhere on Carambolage, some political, some by great unknowns. What follows is are pictures I took while exploring the back of the Zentrum Kreuzberg, entering from Admiralstr.:
I will be returning there periodically to see if anything new has been added, or anything old removed and I'm sure I've overlooked a couple, so keep your eyes peeled for more!