The Catacombs of Paris have been created at the end of the 18th century. In the 1800’s in Paris the cemeteries were overflowing with dead bodies and had become the origin of infection for all the inhabitants. After multiple complaints, the Council of State, by decision of November 9, 1785, pronounced the removal. Beneath the streets were old stone quarries where they had mined stone to build the houses of Paris. So they decided to dig up the overflowing cemeteries and take the bones down into the caverns under the streets and create ossuaries of the the thousands of bones.
credit: waywuwei