Réserve Naturelle de la Galerie du Pont des Pierres

Created in December 1997, it is home to four main species: the Schreibers' miniature, the great rhinolophus, the barbastelle and the little rhinolophus. These species are of high heritage interest at European level, which is why the nature reserve is also designated as a Natura 2000 site. The Pont des Pierres gallery is one of the rare French underground sites that has been the subject of nearly 40 years of monitoring of bat populations.

In 1929, a hydroelectric project required the digging of an underground gallery to partially divert the Valserine river and to benefit from a sufficient drop in the air above the turbines. However, this work was not completed despite almost a kilometre of tunnel being dug into the rock. In 1947, when it was created, Electricité de France inherited the plots and still owns the land today. The project for a hydroelectric power station was never realised.
In 1969, cavers from Bellegarde-sur-Valserine reported the presence of bats in the abandoned gallery. From 1972 onwards, Jean-Louis Rolandez (1954-2004), a speleologist and naturalist, undertook to count the number of bats present several times a year, especially in winter. In 1998, the access to the underground gallery was protected by the installation of grilles allowing the passage of chiropterans.