Cumberland Caverns is a national natural landmark located in Tennessee. It is the second longest cave in Tennessee and one of the longest in the United States. The cave contains many geological formations such as stalagmites, stalactites, and gypsum crystals. Cumberland Caverns was first discovered in 1810 and continues to be explored, with small passages still being found occasionally. Weathering and erosion created the cave over thousands of years by dissolving the limestone bedrock.