© AFP 2016/ Boyan TopaloffThe catacombs are a part of a much larger ancient network of tunnels known as the Mines of Paris.
© AP Photo/ Francois MoriIn this photo taken Tuesday, Oct. 14, 2014, skulls and bones are stacked at the Catacombs in Paris, France.
© Flickr/ Julian FongThe origins of this underground network can be traced to the limestone quarries dating back to the times of the Roman Empire.
© AP Photo/ Michel EulerA man's shadow is seen against one of the walls of the Paris Catacombs.
© AP Photo/ Francois MoriThe catacombs serve as a resting place for the remains of hundreds of thousands of the city's inhabitants.
© AFP 2016/ OLIVIER LABAN-MATTEIPeople visit the section of Paris Catacombs that is open to the public.
© Flickr/ Tobias F. WolfIn the late 18th century the Parisian city authorities began using the catacombs to rebury the remains of the people previously interred at the overpopulated cemetaries within the city limits.
© AFP 2016/ PATRICK KOVARIKMembers of French special police squad "Brigade d'intervention de la compagnie sportive" walk in the Dragon room of the catacombs of Paris. August 20, 2009.
© Flickr/ Jules.BranOnly a small fraction of the catacombs network is open to the public, though it doesn't stop thrill-seekers and amateur spelunkers from exploring the subterranean complex illegally.
© TridekkerThe Catacombs of Paris.
© Flickr/ dapogApproximately 300 Cataphiles - urban explorers who illegally tour the Mines of Paris - enter the network each week via hidden entrances, according to some estimates.
© AP Photo/ Francois MoriSkulls and bones are stacked at the Catacombs in Paris, France. October 14, 2014.
© Flickr/ Tammy O.
Ville Lumière does not translate into City of Lights, but into Light City, meaning it is a place that irradiates light, such as in the form of art and science.