Underground caverns and caves have been eroded into the surface of the earth for millions of years.  The forces of water erosion has formed many of these amazing spectacles all over North America.  The natural underground chamber in a hillside or a cliff is known as a Cave. Caves only have one opening, where Caverns may have several openings.  Underground Caverns have formations known as Speleothems.  The shape that the Speleothems take is determined by the dripping of the water and the flow of the water that enters the cavern.