Mauerpark was created from an area of what had been the death strip following the course of Schwedter Straße.
There's a gentle slope at the eastern edge, just beyond the Max-Schmeling-Halle. I've seen children (and adults too, actually) sledge down it when the snow's thick enough, but it isn't today; the children are all still in school right now anyway.
At the top, bordering on the Friedrich-Jahn-Stadion, is a section of Hinterlandmauer, which has been designated as an area for graffiti:
At the southern end of Mauerpark is Bernauer Straße. Here, the wall turned west and formed what is perhaps one of its most famous stretches. Of course if you head east instead, down Eberswalder Straße, you reach Konnopke's Imbiß. It's lunch time.