A long time ago, on a night, a group of six teenage girls and boys sneaked into the basement of the ministry of telecommunications by following a cable in a tunnel. Upon finding the building quite deserted, they stole a copy of each map of the citywide network of tunnels and walked out of the unguarded front door when they were done. Years later, they turned one of the hidden chambers into a movie theater that can only be described as a fantasy for any movie lover. Read on to find out about this secret underground theater and the mysterious group that built it.

In September 2004, during a training exercise in uncharted parts of the catacombs of Paris, the police discovered a secret fully equipped cinema that could house 20 viewers, a fully-stocked bar, a dining room, and a series of saloons along with professionally installed electricity and three telephone lines. 

When the Parisian police entered the catacombs under Palais de Chaillot, a building once home to Cinémathèque Française, they first saw a sign that said “Building site, no access”. When they went further, they found a camera that recorded anyone who passed and when they got closer to it, a recording of dogs barking was triggered. As they went further, they came into a 400 square meter cavern that contained the cinema and other fully functioning facilities. There were also a giant screen, projector, chairs, films ranging from noir thrillers from the 1950s to modern ones. Moreover, the film lovers had held film festivals in there for many years.

It was built by Les UX (the Urban eXperiment), an underground organization that secretly improves and restores hidden corners of Paris that are historically significant but fallen into repair because the government lacked funds. Around 100 of its members are highly skilled artists, architects, historians, and citizens with technical know-how. 

The UX has carried out many secret projects since its inception in September 1981 when the founders stole the plans of many underground passageways and tunnels in Paris. One of their projects is the restoration of the defunct Wagner clock from the 19th century in Pantheon right under the noses of the police and passersby. Whenever a policeman asked questions, they would flash an official-looking badge with a photograph, hologram of the Pantheon building, a microchip, and a barcode. The group has also restored much of the underground infrastructure and they are responsible for over a dozen other projects which the French government chose not to do for lack of funds.

Three days later, when the police returned with experts from the French Board of Electricity for the formal investigation and to find out where the power came from, they found the cables cut and a note that said: “Ne cherchez pas” (“Do not search”).

Though Paris is famous for its underground tunnels and catacombs, only a small area of it is open to public access. The tunnels were once quarries with full of limestone in the outskirts of Paris. In time, the city expanded to a point where those quarries were beneath it, and about 200 miles of labyrinthine tunnels are believed to exist.

The UX membership is by invitation only and it is received by anyone who is already doing UX-like activities. The members spend on the restorations out of their own pockets. They are highly secretive about the projects and the ones revealed to the public so far were inadvertent consequences. 

Two of the UX’s projects revealed so far are the Pantheon clock and the underground cinema. In the case of the cinema, it was a bitter ex-girlfriend of one of the members who told the police. After the restoration of the Pantheon clock, the group made the mistake of notifying the building’s director, who was more shocked than being happy and hired a clockmaker to re-sabotage it to its previous state. Though they expected the authorities to happily take credit for these projects, charges were brought against four of its members who restored the clock. The judge, of course, ruled in the group’s favor, with one of the government’s prosecutors referring to the charges as “stupid”.

[sources: Wired, Wikipedia, atlasobscura.com]