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.

[2][4] In the Gallo-Roman period, the Fosse Dionne was used to supply water to the Oppidum of Tornodurum built on the Vieux Châteaux plateau overlooking the commune.

[citation needed] The oldest reference to the spring is in an account of the life and miracles of St Jean de Rèome (d. 639) written in 659.

[citation needed] Petitjehan drew on good sources[weasel words] to write his "Description of the old modern and new city of Tonnerre, antiques of the hospital churches and abbeys and estans, etc.".

Finally, it extracts from the great chronicles (notably that of Gregory of Tours) all the references to the ancient commune of Tonnerre.

The washerwomen were protected from the weather by a roof in the form of a “half rotunda” supported by a framework abutting a rubble wall.

The flooded cave has been explored by divers despite the difficulties created by narrow passages and a succession of deep siphons requiring frequent decompression stops.