The first (and one of the best!) thing we did in Berlin was to visit the Turkish market between Kreuzberg and Neukölln. The atmosphere was exotic and hectic and positive and I just couldn't keep from smiling.
We bought sooo much food to bring home. Mangos, oranges, grapes, feta cheese, tomatoes, Turkish bread, humus and much more.
It's there every Friday and Tuesday from noon - 6 PM. The street's called Maybachufer, it's right by the water. Take the U-Bahn (U8) to Schönleinstraße and just go straight north from there! You should really do it when in Berlin.
And this is what we ended up with back home.. best.. dinner.. ever!