Tianchi fills the caldera at the summit of Changbaishan and lies along the China–North Korea boundary. On the northern side, water descends through Changbai Waterfall into the Erdaobai River. The north-slope visitor route is in Antu County, while the wider mountain and its management area extend across several counties and jurisdictions.
The crater lake at Changbai Mountain, ringed by steep volcanic ridges.
Tianchi fills Changbaishan’s summit caldera. UNESCO’s Geopark account describes the lake’s accumulation after an earlier eruption and its refill after the Millennium Eruption.