The catacombs were originally underground limestone mines. Paris is built from the stones mined in these quarries that started back in Roman times. The problems came in the late 1700s when urban expansion meant the city had been built over existing mines. A couple of street collapses drove the government to undertake a project in 1777 to inspect the quarries and built supports to prevent the city from collapsing.
In 1786, there was a health problem with the overcrowded cemeteries within the city limits. It was decided that the underground quarries would make an excellent resting place for the bones from the cemeteries and another project was undertaken to move some 6 million dead people to their new home.This continued until 1859. The transfers were all done at night and escorted by priests.
This engraving on the wall gives the support ID number, the initial of the builder and the date of it's construction.
You can also see the names of streets above engraved in some walls.
This carving was done to memorialize a builder who was killed in a cave in.
Stacking the bones. It looks as if a retaining wall was built with leg bones and skulls. Behind this wall there is a jumble of bones.
Each section has a plaque that tells where the bones came from. These came from the Ancient Cemetery of St Laurent. The bones were first deposited in the Ossuary of the West and then transferred here in 1859.
They got pretty good at bone stacking
And they had a lot of bones.