The Paris Catacombs has its roots all the way back to the 1700s. It was late in the 18th century that the city was facing a public health catastrophe because of overcrowded graveyards leading to water contamination and the spread of disease. To combat the problem, between 1786 and 1814, human remains from the city's cemeteries were exhumed and brought to these underground limestone quarries.
Here you can make your way down nearly two kilometres of passageways, where you'll walk amid skeletal remains that are arranged around memorial plaques according to the type of bone. Some of the bones here date back to before the French Revolution.
To make your way inside, you must head down 130 steps and then voyage through a series of dimly lit tunnels. Note the intricately designed carvings on the walls, known as the Sculptures of Decure, which date back to 1777. These carvings were made by an army veteran as well as a quarry inspector, who lost his level when a sinkhole opened on one of the tunnels' upper levels.
To explore the catacombs, you can pick up an audio tour which will take you through the passageways and give you a real insight into the best bits of the ossuary. This will take you past the Fountain of Samaritan, a small spring surrounded by a wall made of bones. You'll also see the old Sepulchral Lamp which the quarrymen used to light the tunnels when they were working here.
You could spend at least an hour wandering through the tunnels. The catacombs are open daily except on Mondays. Bear in mind that under-14s must be accompanied by an adult.
When you arrive at the Paris Catacombs, you will have to make your way in through an entrance concealed by trees on the Place Denfert-Rochereau. Parking is available nearby for a fee, and public transport stops in the area too. Be warned though, it can be cool underground even in the warmer months so it's wise to take a sweater with you. Conditions can also be slippery, so take care on the stairs, and stay on track -- there are nearly 300 kilometres of tunnels beyond those that are open to visitors, so don't lose yourself!