Emerald calcium lakes discovered in Hang Thang Cave

A multi-tiered system of emerald-colored calcium lakes has been discovered within Hang Thang Cave, located in the core zone of Phong Nha-Ke Bang National Park. The lakes, which cover an area of up to 500 square meters, were first observed in October 2026 following the onset of the rainy season.

According to Le Luu Dung, Director of Jungle Boss Co., Ltd., the cave had been under survey since June 2026, but the mineral pools only became visible when rainwater accumulated. The natural calcium carbonate deposits have formed tiered ridges that act as barriers, creating a series of interconnected pools that reflect the surrounding stalactites and rock formations.

These seasonal lakes typically form around October and can persist until March, depending on rainfall and drainage. The discovery is part of a 15km exploration route that includes Hang Thang and Tra Ang water cave.