These caves, which often served as a sanctuary for refugees (French Revolution, different wars), are former marl quarries which were used in Roman times. Parts of them have been brought back to life via a sound and light show. The sedimentary rock found here is home to numerous fossils and its walls are covered with drawings in charcoal or bas-reliefs, some depicting animals from which fossils have been found (mosasaurus), others based on artistic (Mona Lisa) or religious subjects.