A place where I spend some time almost everyday is the Marheineke Markthalle on Bergmannstraße in Kreuzberg. It's just around the corner from where I live and a great place to buy fresh food and products from local farmers or all kinds of delicatessen from different countries. Many market stalls also sell freshly prepared food and it's always busy at lunchtime. For saturday mornings try the original french croissants.
Just until recently this place used to be one big old Aphoteke (Pharmacy). They have kept the Apotheke's dark wood Art Deco charm to use in benefit of great coffee and fantastic brunch (try the french toast and you'll see I'm not lying).
What’s not to like about The Sammlung Boros Collection? It’s a brilliant private collection of contemporary art held captive in a monstrous, symmetrical ex-Nazi bunker with two metre thick concrete walls, dominating an area of a thousand metres squared. It also doubled as a hardcore techno and fetish club in the ‘90s, of which traces linger in every corner.