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Tonnerre, Yonne – France.

During the Roman era, Tonnerre was known as Tornodurum, which was derived from the Lingone word for “fortress”. It was the capital of Pagus Tornodorensis. Here, in the valley of the Armançon, the County of Tonnerre was created, which served as a point of passage between Paris and Dijon, during a time when the King of France had designs on the Duchy of Burgundy.

Three etymologies of Tonnerre are rooted in the Celtic era: it is derived from Torn an obscure local deity; others claim it is from Douros, meaning fortress; yet others say it is connected to a place near the torrent. It is equally likely that the three solutions are one:

(a) In 1782, newly discovered caves yielded weapons, ornaments, coins, and jewelry linked to the worship of deities; (b) The dominant fortress of Tonnerre was located upon the sites “Mont Bellant” and “Vieux Châteaux” which yield many ancient artifacts;  (c) Amongst the overwhelming evidence of the area’s religious heritage is the Fosse Dionne. Link

Walking around the area in August 2021 – still in the Covid-19 but rules were slightly relaxed under certain conditions – there were not many tourists and if I recalled well, many had chosen to go to the mountains and or the beach for their summer vacation. There were many small alleys here and there and they were almost uphill! Along the way there were interesting buildings, too.

One of the main must-see monument is “La Fosse Dionne” . The Fosse Dionne is a hydrogeological focal point and resurgent spring. It is fed mainly by the rainwater entering the Jurassic limestone layers of the karstic plateau surrounding Tonnerre. Dye tracing studies have demonstrated that some of the spring’s water comes from the Laigne River which disappears underground in the Gouffre de la Garenne at Villaines-en-Duesmois, 43.5 kilometres (27.0 mi) from Tonnerre. The average flow rate is 311 litres per second, but in periods of flood (such as on 15 March 2001) it can reach 3000 litres per second. The average flow varies between 87 litres per second in August and 619 litres per second in January. Link

La Fosse Dionne can be reached by different sides –

And here is the lovely “La Fosse Dionne” in all her splendor and mystery

End of the morning walk and the pigeons bade you “au revoir ” and see you again soon




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