The Perforating Mexicans
In 2004, French police were training in an uncharted section of the Paris Catacombs when they happened upon a secret room deep beneath the city. Unlike most chambers in the catacombs, which are filled only with dirt and ancient bones, this had been turned into a movie theater and restaurant, complete with electricity and a couscous maker.
It seems a group of enterprising Parisians had combined their love of subterranean spaces with their passion for the cinema and created a movie theater in a forbidden part of the catacombs. When the authorities finally arrived for a formal investigation, they found nothing left but a note that read, “Do not try to find us.”
No one has heard from The Perforating Mexicans since, but I have a hunch that they haven’t abandoned the catacombs altogether.
For more information, see the Wikipedia entry, which includes an interesting picture of the secret society at play.