Cave of the Mounds

The Cave of the Mounds is one of the most significant caves in the Midwestern United States. The cave was believed to have formed nearly a million years ago, while the limestone encrustations around it are said to date back over 488 million years to the Ordovician Period. The cave was discovered by limestone quarry workers in 1939 and was opened to the public as a show cave in 1940. Particularly renowned for its brilliantly-colored rock formations, the cave's insides are admirably embellished with everything from Soda Straws, Flowstones and Curtains to Lily pads, Helictites, and Oolites. The formations obtain their resplendent colors from their varying contents of iron and manganese oxides.