Water, Stone, Vine...
Frequently asked questions
How old is Tonnerre?
In 2005, research at Les Petits Ovis revealed that the site was occupied by a necropolis dating from the late Bronze Age and an agglomerated settlement dating from the Second Iron Age.
At Terre de Vauplaine, burials and cremations dating from between the Bronze and Iron Ages were uncovered. A Gallo-Roman rural settlement, known but poorly located, was also identified.
What is the water flow rate in Fosse Dionne?
The Fosse Dionne is remarkable for its flow rate (on average 300 liters per second) and the size of its hydrogeological network, which extends over 40 km.
how deep is the dionne pit?
The spring forms a deep basin (hence the name pit) into which emerges a flooded gallery whose 2.5-metre-high entrance is visible from the outside. The underground hydrogeological network has been explored by divers, despite the difficulties created by narrow passages and a succession of deep siphons requiring frequent decompression stops. The first known exploration was carried out in 1955.
The gallery first sinks at a 45º angle to a depth of 32 metres.
To continue exploration, a 0.80 m x 0.40 m cat-floor must be crossed.
The gallery then rises twice to depths close to 0 metres, before gradually sinking to -70 metres, 370 metres from the limit entrance reached by divers to date. Following a number of fatal accidents, underground diving in the Fosse Dionne is strictly regulated.