The Corveissiat cave and retreat was awarded the "ENS" label by the Ain Department in 2014. Real natural and landscape jewels of the Department of Ain, the sites benefiting from the ENS "Sensitive Natural Areas" label are managed in such a way as to preserve the biodiversity that they host and are developed for opening to the public (with some exceptions due to the fragility of the environments).
The mountains of the Ain, which are generally limestone, are split, fractured, bent and folded on all sides. Over the centuries, run-off water has infiltrated the rock, slowly growing these cracks, which gradually become structured into an underground network of galleries and cavities.
These landscapes are one of the major characteristics of the natural heritage of the Ain.
On the surface, they model fissures, dolines, losses and chasms. A particularly rare fauna is associated with this type of landscape (birds of prey and rock birds among others).