The Paris Catacombs, the massive underground ossuary which attracts hundreds of thousands of tourists a year, are once again the focus a television series.
Here are five things to know about the final resting place for several million Parisians, which are featured in 'Money Heist: Berlin’ which airs on Netflix, as they were before in "The Walking Dead: Daryl Dixon’ and ‘Lupin.’
300 kilometres of galleries
A vast underground labyrinth of narrow tunnels and chambers extends for nearly 300 kilometres on the Left Bank of the River Seine, dozens of metres deep and in some places built on several levels.
They were originally quarries, dating back to the 17th century, from where limestone was extracted to construct buildings in the capital, and gypsum to make plaster.
Skull and bones
About 100 kilometres of these disused quarries were carefully stacked with bones taken from the city's overflowing cemeteries from the end of the 18th century.
The authorities considered the cemeteries, containing Parisians who died between the 10th and 18th centuries, a health hazard.
550,000 visitors a year
The catacombs are one of the City of Light's more macabre tourist attractions.
In 1809 they were opened to the public by appointment, welcoming Napoleon III in 1860 and even a clandestine classical concert with musicians from the Paris Opera in 1897.
Today they are open to all, and welcome 550,000 visitors a year over an area of 1,500 metres.
That's just a small part of the underground network, the rest being off-limits to visitors.
Cata-cops and cataphiles
The banned tunnels and chambers are regularly patrolled by police, known locally as "cataflics" (cata-cops).
They come up against a diehard underworld of "cataphiles" who manage to sneak into the forbidden area via sewers, manholes and metro stations, though they face a fine if caught.
They include those who go underground to party or paint graffiti, or are "catasprints" who explore the network wearing headlamps. Devoted "cata-cleans" clean up after the parties.
Lost and stolen
Inexperienced visitors often lose their way: in 2017, two teenagers were found in a state of hypothermia, after being lost in the maze for more than three days.
The same year intrepid robbers drilled through a wall of the catacombs into a neighbouring wine cellar and made off with more than 300 bottles of the best wines worth 250,000 euros (about R5.1-million).