Urban and underground exploration is a subject that fires my imagination. If you have never heard of it, the practitioners want to explore abandoned buildings, they want to know what's behind all those funny little doors that you may have seen in canal bridges, railway bridges, public parkland, private walls, public places, road bridges - they want to know what's behind the doors marked private.
One such place they have 'discovered' is a buried street in Bristol in the Laurence Hill area. Supposedly you lift a man-hole cover, and in you go. There you'll find old victorian shops with intact gas-lights. Unfortunatelty, the man-hole cover is outside a pub, on a fast main-road, so access is not supposed to be easy. Other reports say the access is from inside the pub itself.
But there are lots of these types of hidden/forgotten places. One story that intrigued me was when Police in Paris recently discovered a fully equipped cinema-cum-restaurant in a large and previously uncharted cavern underneath the capital's chic 16th arrondissement.
Members of the force's sports squad, responsible - among other tasks - for policing the 170 miles of tunnels, caves, galleries and catacombs that underlie large parts of Paris, stumbled on the complex while on a training exercise beneath the Palais de Chaillot, across the Seine from the Eiffel Tower.
After entering the network through a drain next to the Trocadero, the officers came across a tarpaulin marked: Building site, No access.
Behind that, a tunnel held a desk and a closed-circuit TV camera set to automatically record images of anyone passing. The mechanism also triggered a tape of dogs barking, "clearly designed to frighten people off," the spokesman said.
Further along, the tunnel opened into a vast 400 sq metre cave some 18m underground, like an underground amphitheatre, with terraces cut into the rock and chairs.
There the police found a full-sized cinema screen, projection equipment, and tapes of a wide variety of films, including 1950s film noir classics and more recent thrillers. None of the films were banned or even offensive, the spokesman said.
A smaller cave next door had been turned into an informal restaurant and bar.
The whole thing ran off a professionally installed electricity system and there were at least three phone lines down there.
Three days later, when the police returned accompanied by experts from the French electricity board to see where the power was coming from, the phone and electricity lines had been cut and a note was lying in the middle of the floor: "Do not," it said, "try to find us."
There's a wealth of material in this subject, and I've got an idea for another novel brewing away.