April 18, 2016. The inside view of an ice cave in Ningwu County, north China's Shanxi Province. The ice cave in Ningwu, with a history of over three million years, provides remarkable spectacle of icicles, icefalls and ice stalagmites to visitors. Photo: Xinhua

April 18, 2016. The inside view of an ice cave in Ningwu County, north China's Shanxi Province. The ice cave in Ningwu, with a history of over three million years, provides remarkable spectacle of icicles, icefalls and ice stalagmites to visitors. Photo: Xinhua 

April 18, 2016. The inside view of an ice cave in Ningwu County, north China's Shanxi Province. The ice cave in Ningwu, with a history of over three million years, provides remarkable spectacle of icicles, icefalls and ice stalagmites to visitors. Photo: Xinhua

April 18, 2016. The inside view of an ice cave in Ningwu County, north China's Shanxi Province. The ice cave in Ningwu, with a history of over three million years, provides remarkable spectacle of icicles, icefalls and ice stalagmites to visitors. Photo: Xinhua