The limestone rock around Baume-les-Messieurs is pierced with caves which descend 393 feet (120 meters) underground and extend over 0.6 mile (1 km) of developed galleries. These cavities representing the largest group of caves in Jura follow one another with rooms 65 to 262 feet (20 to 80 meters) high, an underground river and lake. They form an ideal habitat for bats and blind cave shrimps of the Niphargus type.