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Tonnerre, Yonne, Bourgogne-Franche-Comté

Discovering Fosse Dionne, in the city of Tonnerre, is both a fascinating and an intriguing experience. Its emerald and turquoise waters, where trouts swim, sparkle in the shade of geraniums and the wash house. More than a simple curiosity, this Vaucluse spring is a natural enigma which explorers have been looking to explain since the 19th century.
© Hervé Lenain / hemis.fr

Tonnerre, Yonne, Bourgogne-Franche-Comté03
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Located in the historic centre of Tonnerre, the karst spring of Fosse Dionne is a natural enigma. As early as Antiquity, homes and people gathered around this mysterious place, before being turned into a wash house with a semi-circular roof in 1758. Its water, shape, and depth continue to intrigue visitors, keeping the spring’s origin secret. This air of mystery has always fed legends and numerous explorations. Pierre-Éric Desseigne, a professional diver, even says it is a magical spot, a kind of passage to another world. While Fosse Dionne is a must-see in the Yonne region, the town and surrounding forest also offer a surprising cultural and historic heritage: the unique architecture of the Hôtel Dieu, built in 1293, and which was a model for that of Beaune, as well as the 12th-century church of Saint-Pierre, which overlooks the town. Explore its half-timbered houses and visit the 12th-century church of Notre-Dame. You will be seduced by its natural charm and gentle living along the waters of the Burgundy Canal.