Tiānchí Lake in Chinese and Heaven Lake in Korean 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 and partly in Jilin Province, northeastern China.
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.