Icicles hang like suspended threads of a waterfall in the Ningwu county, Shanxi province. The cave with millions of years of history has countless icefalls, stalagmites, and icicles. [Photo/people.com.cn]

Icefalls and icicles glisten in blue. The cave in Ningwu county, Shanxi province, is China's largest ice cave at more than 100 meters deep. [Photo/people.com.cn]