Prater Garten is a biergarten at Kastanienalle Prenzlauer Berg, the best bier, the best ambient for families and groups. It has great food and location, you must go.
www.pratergarten.de at prenzlauerBerg Berlin in the middle of the funky suburb of Berlin (east)
Updates
Visited in Feb 2012based on this recommendation and although beer garden was closed, due to it being winter, the restaurant is a cosy atmosphere with a canteen style ambience. Food was excellent as was the home brewed pilsner. Will visit again in summer as beer garden looked a tempting place to spend a sunny evening.
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