Caves in Tennessee are known for their large chasms, and the pit in Keystone River Cave is no exception. Originally, this cave featured an unassuming entrance. After a short dig, however, a "key" stone was removed, allowing the connection to an underground river. After an long stream-crawl, the cave opens into borehole, eventually converging with another massive river. After the two tributaries combine, the water falls 246' into this enormous room, creating a deafening thundering at the bottom.