This large stone water reservoir is known as La Fontaine St-Pierre, or St. Peter's fountain. This was the most abundant of the many permanent water sources on the mountain. There were a total of 16 natural water sources at Bibracte, allowing a large population to live within the fortified walls. In the 1st century B.C. the citizens of Bibracte built a vast rectangular masonry basin measuring 10 by 20.5 meters that was divided into several compartments. In the Middle Ages a wooden basin was built here, and in the 19th century the Viscount d'Aboville, the proprietor of the mountain, had the current stone basin created.
The fountain has always been associated with curative powers, as evidenced by the large number of bronze Celtic and Gallo-Roman votive offerings found there. This continued up through the 19th century, when nursing mothers would bathe their breasts in the fountain to ensure abundant milk.