Dark tunnels, secret societies, clandestine meetings, railways, war rooms, bomb shelters, political movements, ghost tube stations ... I just love reading stories about what lies beneath cities in the vast underground networks many of them seem to have.
Could it be that the city below the city is more interesting?
When you hear that a secret underground cinema was discovered in Paris last year, then, yes, perhaps what lies beneath is sometimes that bit more fascinating!?
The police, initially wary that it may have been a terrorist squad or dark and perverted cult, gave it the bill of health - though were mystified as to who set it up. A follow-up article in The Guardian revealed that it was an underground art group called La Mexicaine de la Perforation, keen to free-up unused city spaces for free expression. (follow the links, read them, they're fascinating!)
It puts me in mind of London Below in the book Neverwhere by Neil Gaiman - the fiefdoms, rat speakers and metaphoric invisible homeless people of the novel that created its own lore based on London landmarks and mythology. The Angel Islington was a chillingly evil serene looking luminescent being. Old Bailey lived atop buildings and, if I remember rightly, cooked Crow Stew. Knight's Bridge was a feared route where the beautifully named character Anaesthesia disappeared assumed dead ... and you found yourself in a real Court held by a Baron, or was it an Earl, moving through the tube system in a capital that has hyperlinked rooms! Amazing stuff. Puts Chislehurst Caves to shame really.