Catacombs of Paris

By the late 18th century, Paris's central cemeteries — above all Les Innocents, in use since the Middle Ages — had become a genuine public health crisis, with mass graves overflowing and, in 1780, a cellar wall near Les Innocents collapsing under the weight of decomposing remains into a neighbouring basement. The solution, decided in 1786, was to move the bones into the network of disused limestone quarry tunnels already running beneath the city's southern districts, the same stone that had built much of Paris above.

Over decades, the remains of an estimated six million people were transferred into the tunnels, and from the early 1800s onward the ossuary's overseer began arranging the bones into deliberate, often macabre decorative patterns — walls of stacked skulls and femurs, some formed into crosses, hearts and other shapes — turning a practical solution into something closer to a monument. Inscriptions throughout, some centuries old, reflect on mortality in the tone of the era.