The Catacombs of Paris are underground ossuaries in Paris, France, which hold the remains of more than six million people. Built to consolidate Paris's ancient stone quarries, they extend south from the Barrière d'Enfer former city gate; the ossuary was created as part of the effort to eliminate the effects of the city's overflowing cemeteries. Preparation work began shortly after a 1774 series of basement wall collapses around the Holy Innocents' Cemetery added a sense of urgency to the cemetery-eliminating measure, and from 1788, nightly processions of covered wagons transferred remains from most of Paris's cemeteries to a mine shaft opened near the Rue de la Tombe-Issoire .