Probably some 20 friends. Some man the BBQ station, some get some rest in reclining chairs, the others do the plumbing... and at 11:43 or so, I noticed one of the men walking to the bushes to relieve himself.
Wonderful idea. Another testament to the fact that Berlin is a wonderful city. I've been there one month before.
Keeping calm is terrorism against those who want to live in fear.