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.
Wyandotte Caves
The main entrance to Wyandotte Cave is 220 feet (67 m) above the level of the Blue River. Wyandotte Cave is known for its long open passageways and large rooms. With 9.2 miles (14.806 km) of passageways on five levels it is the fifth longest cave in Indiana. Included in its formations is Monument Mountain. At 135 feet (41.148 m) tall, Monument Mountain is considered to be the world's largest underground mountain. Wyandotte Cave is also home to a great many helictites, which are considered rare. The cave is also home to the tallest stalagmite in the world, known as the Pillar of the Constitution, but this is only visible on crawling tours.