Fosse Dionne

Useful Information

Location: 14 Rue de la Fosse Dionne, 89700 Tonnerre.
(47.856596, 3.970641)
Open: no restrictions.
Fee: free.
Classification: KarstKarst Spring KarstVauclusian Spring
Light: n/a
Dimension: Yavg=311 l/s, Ymax=3,000 l/s, L=370 m, VR=67 m.
Guided tours: self guided
Photography: allowed
Accessibility: no
Address: Fosse Dionne, 14 Rue de la Fosse Dionne, 89700 Tonnerre.
Office de Tourisme Chablis, Cure, Yonne & Tonnerrois - Accueil de Tonnerre, 12 Rue Général Campenon, 89700 Tonnerre, Tel: +33-3-86-55-14-48.
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
Please check rates and details directly with the companies in question if you need more recent info.


1758 converted into a wash house by the father of the Chevalier d'Éon.


The Fosse Dionne (Dionne Pool) is a circular deep karst spring with intensive blue colour. It is the source of the river Dionne, named after the Celtic goddess of the spring Divona. Drinking water was the necessary basement of any settlement, and so the existence of the spring was the reason for the settlement in this area and the further development of the town of Tonnerre. The cave behind is a water-filled cave, which reaches twice the same level as the water table, with a small air filled space at the cave ceiling, and then reaches a depth of 67 m which is currently the end of the exploration. Some years ago three cave divers died in the cave, so the municipality has restricted diving activities in the cave.

Beneath being a source of drinking water, the water was also used for washing. It seems the use for drinking was much less important than originally, when in 1758 the spring pool was converted into a lavoir That's a stone wall with stone pools which is optimized for washing clothes. The women of the village came to wash clothes in the continually flowing water, then use soap, and finally rinse them with fresh water. Obviously it's a bad idea to do this right at the spring, as the water becomes dirty and thus cannot be used for drinking any more below. In this case, the pool of the spring was surrounded by a circular wall, surrounded by a shallow ditch where the overflow was used for washing. The room at the ditch was covered by a semicircular enclosure, offering shadow and rain protection to the washing women. A straight channel connects the spring with the Armancon river. Halfway it goes underground, because the city was built on top.