The Paris Catacombs, located twenty meters underground, serve as a historical sanctuary for the remains of millions of Parisians since the 18th century. After five months of preservation work, the site has been improved for the safety and enjoyment of around 600,000 annual visitors. The Catacombs, originally created due to a health crisis in the late 18th century, feature a unique architectural design by Louis-Étienne Héricart de Thury, transforming loose bones into decorative walls. The site opened to the public in 1809 and remains the largest ossuary in the world.