Indian Caverns at Spruce Creek, Pennsylvania, is a horizontal karst cave in Ordovician limestone, estimated to be about 500,000 years old and notable for formations including Giant's Hall, a large rimstone pool, and extensive flowstone. Artifacts show human use as far back as 8000 BC, with later use by Susquehannocks, Algonkian peoples, and Iroquois. Known to settlers by the late eighteenth century and reportedly used by outlaw David Lewis after about 1816, it entered a new era when Harold Aden Wertz Sr. opened it to the public in 1929. For decades it was a major show cave attraction before closing in 2016 and becoming a bat sanctuary in 2017.