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The World’s Longest Cave System

Updated: Mar 26

Stretching at least 426 miles (686 km), the caves in Kentucky's Mammoth Cave National Park are, well, really are mammoth.

Entrance to Mammoth Cave in Kentucky
Entrance to Mammoth Cave | NPS image, Public Domain

Located in south-central Kentucky, the park spans over 52,000 acres (21,000 hectares), and perhaps its most famous feature is the colossal cave system that extends for hundreds of miles beneath the woodlands – it’s not named Mammoth Cave for nothing.

The five-level cave system is the longest in the world, and new caves are continually being discovered. Nearly every type of cave formation is exhibited within the site, which show cases 100 million years of cave-forming action. The complex network of caverns and passages features huge chambers, vertical shafts, stalagmites and stalactites, stunning gypsum flowers, delicate gypsum needles, and rare mirabilite flowers. No other cave system in the world is known to offer such a variety of sulfate minerals.

The caves are carved out of limestone, topped with a layer of sandstone and shale. As the sandstone layer leaks, surface water seeps into the limestone, eroding it and creating a labyrinthine network of caves.

Sharks lived in the area around 330 million years ago, when much of the Mississippi River valley was submerged underwater. Thanks to the protection the caves offer from the elements, fossils, such as those of sharks, tend to be well preserved.

Visitors can explore up to 10 miles (16km) of the caves, but they are not the only attraction that the park offers. Visitors can enjoy numerous activities, such as hiking, biking, camping, horseback riding, fishing, and kayaking.

Officially dedicated as a national park in 1941, Mammoth Cave became a World Heritage Site in 1981 and an International Biosphere Reserve in 1990.

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