An exploration of limestone caves in Illinois begins with Illinois Caverns, the second-largest cave in the state, in Waterloo. Visitors can explore the cave there from April through October. The 118-acre site was purchased by the IDNR in 1985, and it was previously referred to by names such as “Mammoth Cave” or “Burksville Cave.” The only commercially operated cave in Illinois, previous records indicate visitors paid to explore Illinois Caverns as far back as 1901.
The temperature in the cave at Illinois Caverns remains steady at 58 degrees year-round. An underground stream winds through the cave as well. Bats are commonplace, and back in 2010 the cave was closed to the public for over a decade to help slow the spread of a fungus that kills bats. The cave reopened to the public in June 2021. The latest figures show an average of 750 visitors a month to Illinois Caverns, which includes about six miles of mapped passages. There is no entrance fee, but visitors must wear a hard hat and sturdy boots while carrying at least three light sources.
The largest cave in Illinois is in Monroe County and owned by the IDNR. Fogelpole Cave includes a subterranean wilderness, with the Illinois Audubon Society purchasing over 44 acres to help preserve the groundwater basin that drains into Fogelpole. The Fogelpole Cave includes a large and diverse animal population and is among the least-disturbed cave systems in Illinois.
Also in Monroe County is the tiny village of Valmeyer, which was moved to a nearby bluff after the Great Flood of 1993 engulfed the town. Through the process of moving, the village acquired a limestone rock quarry that is now known as Rock City and has become a massive underground business complex. The complex includes warehouse space, food storage space, and provides massive storage space for military and civilian personnel records. Future development in Rock City could involve high tech and computer data centers.
Cave-in-Rock State Park is located in Hardin County in deep southern Illinois on the Ohio River. The Park includes a 55-foot-wide cave carved out of limestone rock by water thousands of years ago.
Deep southern Illinois is also home to Sand Cave, located in the Shawnee National Forest. This landmark is known as the largest sandstone cave in North America, and visitors can access the cave through a walking trail. This remote cave includes a mouth almost 30 feet wide.
Moving to the far northwest part of the state, Mississippi Palisades State Park in Carroll County offers limestone caves, including Twin Sisters and Indian Head. In Kendall County near Chicago, remnants from a limestone cave have provided geologists with excavated fossils to help uncover historical secrets from over 300 million years ago. And along the Kankakee River down I-57 from Chicago sits the Bourbonnais Geologic area. This development, known as the Indian Caves, is located in Perry Farm Park. The small, narrow caves there are accessible for exploration, but entry is available only through a narrow crevice.