Located on the east side of Qixingshan (Mt Seven Star), between the Qingtiangang plateau and Menghuan Lake (Dream Lake), Lengshuikeng (Cold Water Pit) was formed by volcanic lava flowing down from the mountain, forming a barrier lake. The lake was eventually drained leaving the landscape we see today; Lengshuikeng contains Taiwan’s sole bed of precipitated sulfur. Hot spring here belong to the neutral carbon type of spring with a pH of around 6.5 and a temperature around 40C. Although it is substantially lower than other hot springs, as long as it’s about 6 degrees above human temperature, it can still be classified as hot spring.

Sulfurous fumes vented in the bed of this marshy lake turn the water milky. After gradually precipitating, the sulfur forms whitish-yellow-pale gray layers in the lake bed. Popularly known as the “Milk Lake” by the locals, in 1992, Yangmingshan National Park office built 2 free hot spring dipping rooms for the public, and since it is located along the way to the beautiful Qixingshan (Mt Sever Star) and the waterfalls, it has gradually become one of the most favorite tourist attractions.