First opened to the public in 1810, the ‘empire of the dead’ is now illuminated with electricity in its entire length. In the Medieval period, the catacombs were quarries, but towards the 18th Century, as overcrowded cemeteries became a menace to public health, city officials opted to use the catacombs as burial grounds. Thus, the bones of many were moved here. In 1830, the catacombs were closed by the prefect of Paris, as he considered them obscene and indecent. During World War II, the site headquartered the French Resistance.

Over the centuries, the catacombs were used in various ways. Evidence shows that in the 19th Century some families even lived in the catacombs. In the same tunnels, communards killed a group of monarchists in 1871 and German soldiers established an underground bunker during World War II. The bunker is not on the tourist route but those interested in their history should read the famous novel by Victor Hugo , 'Les Misérables', in which they will find a detailed description of the tunnel system.

The underground tunnels and chambers have long posed problems to the safety of ground-level structures in Paris. The quarries sometimes cave in, resulting in a hole above ground and damage to buildings. To prevent this, the Inspection Générale des Carrières (IGC), or General Inspection of the Quarries, was established in 1777 to monitor the present quarries and prohibit the digging of new ones. The IGC dug observation tunnels in order to better monitor and repair the quarries.

Access to the catacombs is restricted, with only a small portion opened to the public. The remaining section of the extensive network, which spans more than 300 kilometres, can be strolled through via an ‘unauthorised visit’. The tunnel system is complex, and even though some tunnels feature plaques indicating the name of the street above, getting lost is very easy. Some passages are low or narrow, while others might be partially flooded. The tunnels are packed with ageing telephone wires and pipes which could hinder progress. Sporadic cave-ins might occur as well. A guide is indispensable, and even the more qualified ones still refer to a map. Owing to the potential perils of an individual unguided visit, accessing the catacombs unescorted by officials was declared illegal in 1955. Today, visitors might escape with a 60 EUR fine if they get caught by the cataflics, special police who patrol the site.

Secret entrances do exist throughout Paris however, and it is possible to access the tunnels through the sewers, metro and certain manholes. Parisians sometimes make use of these access points to meet clandestinely, to hold unusual parties, or merely as urban explorers. Those who have a particular affinity for exploring the tunnels are known as 'cataphiles'. The enigmatic glow of the site is also showcased in numerous fiction narratives. In Umberto Eco’s novel 'Foucaul’s Pendulum', the catacombs are described as the resting place of a parchment concerning The Templars order. In Robison Wells’ novel 'The Counterfeit', the catacombs are the setting of fictitious Illuminati meetings. Edgar Allan Poe’s short story 'The Cask of Amontillado' (1846) has its main character, Montressor, walling up another man inside a cavity, deep within the catacombs, which are depicted as being lined with human remains.