Although it's in the middle of the tourist circuit in Auguststrasse, Clärchen's Ballhaus is still really a special place. A ballroom built in 1913, the building is still wonderfully run-down (they have a tendency to sometimes overly renovate old buildings in Berlin to the point where they loose all their old charm; Tod saniert they call it which is literally "renovated to death".) On the bottom floor is a restaurant (you can also eat in the garden if the weather is nice) and dance floor where they often have a live band.
There are certain dance theme evenings like cha-cha-cha and tango as well as a Tanz Tee (teatime dance) every Sunday afternoon. If you don't know any of the standard dances, they also offer dance classes to help you break in those vintage 1940s dancing shoes....
I've actually only been there once but what I loved about the place was how mixed the crowd was, everything from tourists, to hipsters to old timers decked out in vintage duds.
Upstairs is also the deliciously dilapidated Spiegel Saal (Mirror Ballroom) where they sometimes have concerts. You can also rent the room for private parties. Jasper and I looked into it once. I don't remember what the price was exactly, but I do remember it made my eyes bug out of my head. Not a bargain perhaps, but a night in that room would certainly be one to remember.
Claerchen's Ballhaus, Auguststrasse 24-25, Berlin-Mitte
Open daily from 10 a.m. til whenever
Website: Claerchen's Ballhaus