As another poster said heavy drug use, but also fetish sex.

I've been to parties that have had signs on the bathroom banning acts that would make a vanilla person blush.

There is a lot of heavy drug use.

And there are areas in Berghain that are more like a sex/fetish club than a night club.

"Se non è vero è ben trovato" but this reddit post [1] does a decent enough job of explaining what's happening there (or what cool people think it might be happening in there). Slightly NSFW text post:

[1] https://old.reddit.com/r/redscarepod/comments/11nll0r/my_gir...

No they can't give an example because it's a safe space