Heaven Lake (천지 (Ch'ŏnji or Cheonji) in Korean; 天池 (Tiānchí) in Chinese) is a crater lake on the border between China and North Korea. It lies within a caldera atop the volcanic Baekdu Mountain, a part of the Baekdudaegan mountain range and the Changbai mountain range. It is located partly in Ryanggang Province, North Korea, at 42°00′22″N 128°03′25″E / 42.006°N 128.057°E, and partly in Jilin Province, northeastern China.
Geology and limnology 
The caldera which contains Heaven Lake was created by a major eruption in 969 CE (± 20 years).
The lake has a surface elevation of 2,189.1 m (7,182 ft). The lake covers an area of 9.82 km² (3.79 sq mi) with a south-north length of 4.85 km (3.01 mi) and east-west length of 3.35 kilometres (2.08 mi). The average depth of the lake is 213 m (699 ft) and maximum depth of 384 m (1,260 ft). From mid-October to mid-June, it is typically covered with ice.
Names and legends 
In ancient Chinese literature, Tianchi also refers to Nanming (南冥 sometimes translated as "southern sea").
Some other well-known lakes named Tianchi include those in Xinjiang and Taiwan.
In North Korean legend, Kim Jong-il is claimed to have been born near the lake on the mountain. Upon his death, the Korean Central News Agency claimed that the ice on the lake cracked "so loud, it seemed to shake the Heavens and the Earth."
Lake Tianchi Monster 
believe that the lake is home to the Lake Tianchi Monster.
On September 6, 2007, Zhuo Yongsheng (director of a TV station's news center run by the administration office of the nature reserve at Mount Changbaishan, Jilin), shot a 20-minute video of 6 seal-like, finned "Lake Tianchi Monsters", near the border with the Democratic People's Republic of Korea (DPRK). He sent pictures of the Loch Ness Monster-type creatures to Xinhua's Jilin provincial bureau. One of them showed the creatures swimming in 3 pairs, in parallel. Another showed them together, leaving ripples on the volcanic lake.
See also