The popular site houses the skeletal remains of some six to seven million former Parisians. Not all areas of the Catacombs are open to the public. Back in the late 18th century, cemeteries were becoming over-populated. Cemeteries such as Les Innocents were so stuffed with the dead that it led to improper burials, open graves, and unearthed corpses. Neighbors began getting sick with infectious diseases due to the unhealthy conditions of the cemetery