A few weeks ago I once again descended deep beneath the city, twenty-five meters below ground, to visit the carrieres of Paris. It's my third trip there now, but this time I was in the company of a expert, a specialist in the subject, a man who has made his life's work the study of every kind of man-made tunnel and cave. He is the co-editor of one of the reference works on the subject, and so it was something of a privilege to make this trip. A friend of a friend introduced me to him, and on one fine warm Sunday afternoon we left behind a pleasant Parisian summer afternoon (elegant well-dressed people drinking espressos on terraces, summer sunshine illuminating parks and beautiful broad boulevards, that kind of thing) to descend into the dark and the cold of the Parisian Carrieres.
Some history: there are hundred of kilometers of tunnels here in southern Paris, many of them centuries old. In medieval times, limestone was quarried extensively from deep underground, leaving behind many caves and tunnels. Later, in the 18th century, as the city limits rapidly expanded, suddenly buildings were collapsing, holes opening up in the street. These ancient underground caves had collapsed, the earth had subsided. No-one expected the ground to carry all this weight, after all it was open countryside when they were quarried. This was the origin of the 'inspection des carrieres' (IDC) who joined up all these underground caves and quarries with tunnels, who drew up detailed maps of where everything was. In Paris, the owner of a patch of ground is also the owner of everything down to the level of the carrieres; almost the first operation in any building work here is assessing how solid the ground below actually is -- and reinforcing it if it isn't, which can be expensive.
Over the years, many of the tunnels have been closed off or filled in, but in large part the network still exists, and inspections are still carried out regularly by the IDC- but of course, they are not the only people down there. At one time, almost every public building in Paris boasted a set of staircases going down, an entrance underground; today, most of these entrances have been closed off. But a few still exist...There are manhole covers in the street which go down, but these are for the large part welded shut; but every so often, one will open; some work needs to be done, the manhole cover is opened and ...
There is one way to enter, one way to descend, that has always remained open, more or less. At one time, a railway followed the outskirts of Paris, an outer circle: it was called 'le petit ceinture', or 'little belt'. There are parts of the railway that still exist today, although no passengers have crossed the platforms for perhaps a half-century. In one location, not far from where I write this, a tunnel takes the abandoned railway lines underneath the current tracks of the line four metro. In the middle of this cold, damp tunnel (it is actually underneath the "parc montsouris") there is a hole in the wall -- that hole leads to the carrieres.