As it happens a couple of months later I wandered down to to the flea market at Mauerpark Berlin, which takes its name from the old Berlin wall and death strip that ran across the ground it now occupies. It was late afternoon on a cold fall's day and I looked up to see literally thousands of people sitting on concrete steps in this big amphitheater with karaoke happening down below. It really is crazy. This Irish guy really is set up with a bicycle (check out some of the you tube video below) and invites people up. Now what makes this really stand out is that there was a lot of talent in the bear pit that day. Berlin is filled with musicians and other artistic types struggling to make a go of leading creative lives. So more than a few of those who came up were practiced if not professional performers. There was real improvisation going on, not just people blindly following a bouncing ball lighting up words on a screen. This is a great free thing to do, but even if I had to pay I would have got my money's worth.
The other thing that made this stand out was the crowd. There were easily 2000 people, all enjoying themselves, clapping, cheering and encouraging the performers. Plenty of drink was going around (as well as a few less than legal substances) but everyone was well behaved with great spirit. Most were locals although a fair number of tourists and other visitors were also about. Local market stalls are also in on the act. Some were selling gluhwein, others had sparkles and lights which came out as the sun went down. It happens every Sunday afternoon at Mauerpark, which you can get to easily from the Nordhahnhof station.
I'm tempted to say this is Berlin's best kept secret but it is not much of a secret these days. It is certainly becoming one of Berlin's best attractions and is high on the list great free things to do.