There's a bunch of people, and I don't know if they are the same ones who seem to know all those secret entrances to the Catacombes, but they somehow manage to get to all the good places and I don't know how. Or probably more realistically I don't know 'who'.

Walking through the south of the city near Alésia I came across one of those strange bridges that crosses the rather spooky old disused railway that was called the 'Petit Ceinture' or the 'little belt' which circled the town. And there, sure enough, were a couple of chaps happily strolling along like any other Sunday strollers, except that this walk is not normally open to the public (and it was Saturday, but that's not the point)!

The shot was snapped on the spur of the moment and leaves a lot to be desired with terrible light but you still get the sense of a nice leafy walk but you'd never guess that it was just round the corner from Montparnasse in one of the world's most popular city destinations.

Although I'm dying to do this walk, it must be a bit eerie going through those abandoned tunnels where trains used to chug in days of yesteryear, deep down in the cutting surrounded by ominous high walls and towering buildings. But you'll be the first to know when I do it.