Krubera Cave
The difference in elevation of the cave's entrance and its deepest explored point is . It became the deepest-known cave in the world in 2001 when the expedition of the Ukrainian Speleological Association reached a depth of which exceeded the depth of the previous deepest-known cave, Lamprechtsofen, in the Austrian Alps, by . In 2004, for the first time in the history of speleology, the Ukrainian Speleological Association expedition reached a depth greater than , and explored the cave to . Ukrainian diver Gennadiy Samokhin extended the cave by diving in the terminal sump to 46 metres' depth in 2007 and then to 52 m in 2012, setting successive world records of 2,191 m and 2,197 m, respectively. Krubera is one of the two known caves on Earth deeper than 2,000 metres.
Tuckaleechee Caverns
Tuckaleechee Caverns () is a set of caverns and AAA GEM attraction in Townsend, Tennessee, near the Smoky Mountains. The caverns were discovered in the mid-19th century and were opened to the public by Bill Vananda and Harry Myers in 1953. The caverns are known for the "Big Room", an immense cave/cavern room that a football stadium could fit inside. The caverns have stalagmites reaching 24 feet tall with flow-stone formations hundreds of feet in length and width.
Open MARCH 15 to NOVEMBER 15
Tuckaleechee Caverns also has the tallest underground waterfall in the country named "Silver Falls", a 210-foot two-tier waterfall. The cavern originates at White Oak Sinks in the Great Smoky Mountains National Park. The Caverns host a seismograph system monitored by the United States Department of Defense,CTBTO and the United States Geological Survey (USGS).