The catacombs date back to Roman times, they are ancient limestone and gold quarries. Most of the 5-6 million people buried in there are not catalogued (actually none are, but some have church/dates) because there bodies were buried during epidemics/plagues. In the 1700s the churches of Paris and surrounding areas practically ran out of room in their cemetaries and moved all the current remains into the tunnels, leaving the piles of bones (one pile per church) with no more identification than the average deceased date and the name of the church. The former cemetary remains are the only ones available to be seen close up by the public, some others can be seen through locked bar gates but not approached. No flash is allowed so any photos must be taken with delayed-shutter in the scarce orangish light reflecting off the red/brown bones lining the walls of the catacomb. The image was photoshopped for obvious reasons (levels, contrast, to remove dust/scratches, size ratio for wallpaper), but the eerie color is all natural.