When raves were underground and highly illegal events held in lofts and warehouses they used to have all kinds of fun ways to conceal the location of the party from the police, the most fun being the secret door.
There was something so magical about stepping through an ordinary door into a club full of flashing lights and bumping beats, but what sort of rave would you expect to find on the other side of a porta-potty door?
At the 2017 Sziget Festival in Budapest attendees who knew the inside poop could head to a "secret" rave by entering a specific porta-potty, but as this video by Rave Jungle shows it was more of a gimmick than a well-guarded secret.
-Via Laughing Squid