Lost Property in Chatelet

There is no order for the unprepared who visit Chatelet. Overhead messages suggest that your destination is just around the corner. But when you turn that corner, oh no, a cavernous tunnel stretching as far as the eye can see. Yes, there are moving walkways, but some are treacherous and refuse to move. There are also letters A, B, C. No, there is no trace of C. Disturbingly, the sequence moves from B to D. Where is C? What happened to C? What is this place? Some people may not have seen the light of day for decades. Whole lives are lived in those sweaty chambers and trains smelly metal worms which