In late autumn, Ulan Lake – nestled deep within the Tengger Desert in Alxa League, Inner Mongolia – continues to draw visitors with its mesmerizing palette of colors.

Composed of an irregularly shaped main lake and several smaller satellite lakes, Ulan Lake is rimmed with bright white salt crusts and dotted with crimson patches. From above, the deep red water – resembling a beating heart – creates a striking visual contrast against the pale desert background, earning it the name "Heart of the Earth."

The lake's hues come from halophilic microorganisms such as salt-loving algae and bacteria that thrive in the saline environment. These microorganisms produce pigments like astaxanthin and carotenoids, giving the water its distinctive red coloration. As the lake water evaporates and salinity increases, the color deepens even further, making Ulan Lake a living, pulsating masterpiece at the heart of the desert.