Nickajack Cave is a large, partially flooded cave in Marion County, Tennessee. It was partially flooded by the Tennessee Valley Authority's Nickajack Lake, created by the construction of Nickajack Dam in 1967. The entrance was originally 140 feet wide and 50 feet high. There is now about 25–30 feet of water at the entrance, so the portion of the entrance above water is 140 feet wide and 20–25 feet high. It houses a large colony of Gray Bats, an endangered species, and the water levels have posed a danger to the bat colony. The cave took its name from the Chickamauga Cherokee town of Nicojack/Nickajack, located between its mouth and the Tennessee River. The town was destroyed once in 1794 by the Nickajack Expedition.