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, since the low temperature and frequent snow there. (Photo/China.org.cn)

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, since the low temperature and frequent snow there. (Photo/China.org.cn)

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, since the low temperature and frequent snow there. (Photo/China.org.cn)

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, since the low temperature and frequent snow there. (Photo/China.org.cn)

Landscape of the Changbaishan Mountain in northeast China's Jilin Province in the middle of June. Changbaishan is known as a natural museum for rare plants and animals, rich in ginseng, mink skin and deer (the three are sometimes referred to as the three treasures of northeast China). (Photo/China.org.cn)

Landscape of the Changbaishan Mountain in northeast China's Jilin Province in the middle of June. Changbaishan is known as a natural museum for rare plants and animals, rich in ginseng, mink skin and deer (the three are sometimes referred to as the three treasures of northeast China). (Photo/China.org.cn)