Baumbluetenfest
Hundreds of thousands of visitors come to Werder (Havel) each and every year to celebrate the "Blossom Festival". It's a 30 min ride on the train, just a little further than Potsdam from Berlin.
What you can do there? Well, it's basically about drinking wine :-) There is an amazing variety of fruit wines. I tried "strawberry + rhubarb" and "plum" and it was really good! The festival is the second largest after Oktoberfest in Munich... Can you imagine? :-)
There are also fun fairs and since the weather was really good - to the point of being too hot - my dear friends convinced me to go on the water slide / water roller coaster. Of course we got all wet :-(
Right, gotta take care of my sunburn now...