The Fontaine-de-Vaucluse Chasm
With an average annual discharge totalling 630 million m³, this is the largest river source in France, and one of the largest in the world, in terms of volume discharged.
Cool and peaceful in summer, bubbling and impetuous in spring and autumn, the source, a true whim of nature, has unceasingly intrigued curious visitors and researchers since ancient times.
The source is the result of the re-emergence of water from a vast underground network. The water bubbling out of the ground at Fontaine-de-Vaucluse comes from the infiltration of rainwater and snowmelt from the south of Mont Ventoux, the Vaucluse Mountains and the Montagne de Lure, which form an 'impluvium' of 1,240 km². The only place where this water can come to the surface is precisely at Fontaine-de-Vaucluse.
While visitors gape in astonished wonder at the spectacular floods in spring and autumn (90 m³ per second), the steady flow during summer and the rain-free seasons provides experts with something more of an enigma. Speleologists have highlighted the existence of collectors, veritable natural drains feeding the Fontaine de Vaucluse.
The end of the 19th century saw the first attempt by divers to explore the source's water-filled conduit. Today, thanks to more than a century's worth of bold explorations, we now have a partial understanding of how it all works and where the water comes from.