Mammoth Cave National Park, Kentucky, USA, encompasses part of Mammoth- Flintridge Cave System the longest cave system in the world. It is over twice as long as the second largest cave system, Mexico's Sac Actun underwater cave.
The Reed Flute Cave (China). The cave get’s it’s name from the reeds growing inside that are ideal for flute making. Reed Flute has a gambit of miraculous rock and mineral formations, carbon deposits, and stone pillars.