The World's Longest Cave: The total surveyed extent of Mammoth Cave currently stands at over 412 miles (more than 663 kilometers) with potential for a 1,000 mile (1,600 kilometer) system. In addition, there are more than 200 caves within the park which are disconnected fragments of the larger system or associated with local drainage features. The geology and geography of the area has resulted in a variety of karst basins, which have become the most thoroughly understood conduit flow aquifer in the world.
Karst Landscapes: These regions are characterized by rapid subsurface drainage through limestone and cave systems, accounting for approximately 20% of the Earth's land surface, 25% of the continental United States and 45% of the area east of the Mississippi River. Approximately 40% of the U.S. population relies upon karst aquifers for drinking water.