Velebit caves
The "Lukina jama" cave is 1431 m deep (2013), the deepest cave in Croatia, 14th deepest cave in the world and the deepest cave in southeast Europe. At its foot, there are ponds and streams including one of the largest known colonies of subterranean leeches ("Erpobdella mestrovi"), which has been ascertained to represent a new species, genus and also family. Other species discovered in the system, include the air-breathing land snails "Zospeum tholussum". Like Lukina jama, Slovacka jama, Velebita and Meduza are also located at the "Hajdučki i Rožanski kukovi" special reserve, a dedicated part of the Sjeverni Velebit national park.
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).