The Ammonite Fossil Rock-Slab is one of the emblematic sites of the Geopark. Classified as a National Geological Nature Reserve, it is managed by the County Council.

Over a surface area of about 300m2, more than 1,500 ammonites have been counted. Some are large, others are fragments, but more than 90% of them belong to a single species: Coroniceras Muticostatum, which dates from the Sinemurian stage, a stage of the Lower Jurassic period between 200 and 190 million years ago.