Today we moved some boxes and other junk from the office into the 'cave' or cellar beneath the building. This was the first time I'd been down there, and Pascal, who originally found the offices for us, lead the way.
The timer on the cellar light had a ridiculously short fuse, and several times we were plunged into darkness and had to scrape along the walls to find the (unlit) light switch. Pascal wanted to show me something in particular, although it meant dashing down a corridor for a brief look before having to dash back again before the lights went out.
It was a tunnel leading even further down than the cellar, and was an entrance to the Paris catacombs! The catacombs near the Denfert-Rochereau metro are fairly well known, since tourists can enter them, and more significantly since they've been used as an ossurary after the cemetaries of Paris started to overflow. For about a kilometer the tunnels are lined with skulls and thigh bones (well worth a visit, especially if you tell your guests it's really a mass grave from the revolution).
Less well known are the rest of the catacombs - some 300km in length! A friend first told me about them five years ago, as a flatmate of his was a 'cataphile' and regularly explored the miles of tunnels. Totally illegal, with a 60€ fine if you stumble into a policeman down there (which is sooo likely of course). There are websites (apparently - go google) with maps and other hints & tips for the wanabee cataphile.
So, this was an entrance to the tunnels - it was amazingly atmospheric. The light seemed to stop right there at the entrance, making it literally a black hole. Not that we went in, that'll wait until we're drunk and stupid one night...