People ascend stairs in underground cavern. Mammoth Cave National Park, Kentucky, USA.
Tourists ascend a stairway in Mammoth Cave National Park, which was established in 1941 in Edmonson County, Kentucky, USA and was declared a UNESCO World Heritage Site in 1981 and international Biosphere Reserve 1990. With over 390 miles (630 km) of passageways, the Mammoth-Flint Ridge Cave System is the longest known in the world. Mammoth Cave developed in thick Mississippian-aged limestone strata capped by a layer of Big Clifty Sandstone. Descending limestone layers include the Girkin Formation, Saint Genevieve Limestone, and Saint Louis Limestone.Add to Cart Add to Lightbox Download