At the end of the 18th century rampant disease in the Les Halles neighborhood caused by the adjacent Cemetery of the Innocents led to the mass grave being entirely exhumed. In 1785 it was decided that the bones were to be moved to the building stone quarry under the Montsouris plain in the south of Paris. On April 7th, 1786, after being properly converted and readied, the quarries were consecrated and became the principal ossuary of Paris.
Until 1788, cartloads covered in black drapes, escorted by priests chanting the Office For The Dead, crossed Paris by night to deposit their remains.
Originally, the bones were simply dumped. Louis-Etienne François Héricart de Thury, Engineer-in-Chief of Mines, had the bones rearranged artistically and made the galleries accessible to the public in 1810. The result is what you see here: thousands, perhaps millions, of skeletons, their constituent parts sorted and neatly stacked, the various collections marked to indicate which cemetery originally held the remains.