Ohio Caverns

Ohio Caverns is a show cave located 30 miles (48 km) from Dayton, Ohio near West Liberty, in Salem Township, Champaign County, Ohio in the United States. A popular tourist destination and member of the National Caving Association, it is the largest of all the cave systems in Ohio and contains many crystal formations. Approximately 90% of its stalactite and stalagmite formations are still active. The cavern system was originally an aquifer, holding an underground river of melted glacier water. This river eventually receded to lower levels of the ground and is now unseen.

Cave data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).