The zero kilometre of the Marne, the longest river in France (500 kilometres), is located under the porch of a modest fountain built in 1877. The water of this spring comes from a network of active karstic galleries, partially explored by speleologists. The natural outlet of the underground river is currently hidden by scree covering the base of the Bajocian ledge.
A recent development (1956), of the draining gallery type, makes it possible to capture the flow circulating under the scree in order to supply drinking water to the village of Balesmes situated below.
The Marne River flows into the Seine, after having completed a quarter of its course in Haute-Marne and crossed five departments.
This spring borders another natural site: the Grotte de Sabinus, named after a Gallic chief who took refuge in this cave after fighting the Romans.

This legendary place offers a marvellous panorama, and interpreted paths lead through the rocks to the spring.