Courage is a little cafe just up the road from the world famous Circus Hostel. It's cramped and dark with a fantastic atmosphere and even better beer. The menu is ridiculously low budget, firm favourites of mine are the steak with roast vegetables and ice und heiss - ice cream with hot summer berries. A real find.
Just off Rose Luxemborg Platz
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The exact address is Saarbrücker Strasse 17. Just off Rosa-Luxemburg-Platz is right, although a better description is "near the south exit of 'Senefelder Platz' station" (same U-Bahn line as Rosa-Luxemburg-Platz: U2).