This nat­ur­al lime­stone ice cave is the largest of its kind, extend­ing 42 kilo­me­ters into the earth and wel­com­ing 200,000 tourists every year. Although the cave is mas­sive, only the first kilo­me­ter of it is cov­ered in ice and open to tourists. The rest of the cave is just lime­stone. The old­est lay­er of ice in the cave dates back 1,000 years!