“Nobody knows where the water comes from”, this immense natural pit has intrigued for centuries

This water source in Burgundy conceals a great mystery era: no one has ever found its origin!

Haunted castles and forests, abandoned houses, bottomless lakes, mysterious rocks… France is full of places, each more enigmatic than the last. Did you know that there is a gigantic old washhouse in France, the scene of tragic events, whose source remains unknown to this day ?

In the city center of Tonnerre, a small town of character in Burgundy, the Fosse Dionne holds many secrets. Its deep turquoise waters flow to the surface all year round, resulting from underground flows whose origin has never yet been discovered, giving rise to multiple explorations and legends… "This kind of small corridor that opens onto another world that is the Fosse Dionne, is a magical place", exclaimed in 2021 the underground diving specialist Pierre-Éric Desseigne at TF1, which had obtained authorization in 2018 to dive into the pit to find its origin, in vain.

The first attempts to explore the pit date back to the 19th century, most of which resulted in tragedies: in 1962, two speleologists found death there. 32 meters deep and in 1996, the death of a diver descending to 70 meters led to a diving ban. Since 2018, filmed diving has been permitted to a depth of 80 meters, 370 meters from the water surface.

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While the mystery of its source has never been solved, many objects have been found there. found such as glass pipes and ashtrays. “I imagined the person 200 or 300 years ago who smoked this pipe and threw it into the water. There is also the beauty of the gallery, of the contrasting rock because there are some quite dark ones and then there are very light clay carpets,” says Pierre-Éric Desseigne, TF1. 

This spring, already venerated in Antiquity under the name of Fons Divina, was transformed into a washhouse in the Middle Ages by the mayor of the city Louis d'Eacute;on. Since then, the mystery of the Fosse Dionne has fueled legends that span the centuries: the oldest dates back to the 6th century AD and refers to a snake that kills the inhabitants of Tonnerre when it comes out of hiding, by the sheer force of its gaze.

In the year 700, it is said that the bottom of the basin became the depths of hell when the devil threw himself into it after trying to to corrupt the soul of a child with gold coins. The most recent legend tells that one moonless night, a young girl about to be overtaken by a demon implored the Virgin to come to her aid. The Virgin then appeared in a large emerald cloak and dragged the young girl into this vast crater filled with water to save her from the devil.

Even today, the Fosse Dionne leads some locals and tourists to believe that its creation is of celestial or diabolical origin… Head to the Yonne if you want to discover this immense washhouse, 14 meters in diameter, with its strange green color. Disquieting atmosphere guaranteed.