From the World Heritage inscription for Mammoth Cave National Park:
Mammoth Cave is the most extensive cave system in the world, with over 285 miles (456 km) of surveyed cave passageways within the property (and at least another 80 miles [128 km] outside the property). The park illustrates a number of stages of the Earth’s evolutionary history and contains ongoing geological processes and unique wildlife. It is renowned for its size and vast network of extremely large horizontal passages and vertical shafts. Nearly every type of cave formation is known within the site, the product of karst topography. The flora and fauna of Mammoth Cave is the richest cave-dwelling wildlife known, with more than 130 species within the cave system.
Mammoth Cave is the biggest cave system in the world. From a photography perspective, it is also the most boring. Given the way the cave system was formed, it doesn’t have much in the way of the majestic stalagmites or stalactites you see in other caves. I took over 200 photos in Mammoth Cave and walked away with 12 that were any good, and 4 of those were taken above ground. As an added kicker, they do not allow you to bring a tripod in the cave, which makes photography just a wee bit tricky.
View the complete list of UNESCO World Heritage Sites in the United States.
View the list of all of the UNESCO World Heritage sites I have visited on my travels.