The frozen Tianchi Lake, a lake at the mouth of Changbaishan Volcano, is seen on the Changbaishan Mountain in northeast China's Jilin Province in the middle of June. The lake water is superbly clear, as blue as sapphire, but only can be seen during the summer time, usually from late June to August, because of the low temperature and frequent snow there. [Photo by Zhang Tingting / China.org.cn]