2. Travertine ponds: Formed by a long-time sedimentation of the travertine in the karst fissure water, appearing in eight groups from the lower to the upper reaches.

3. Travertine waterfalls: A kind of vertically streamlined sedimentation of travertine, such as the Bathing Cave Waterfall, which is 33 meters wide and 6.7-7.3 meters high.

4. Travertine caves: Formed when travertine substances are eroded by underground water, and later sink. There are three travertine caves in Huanglong Valley: Huanglong Cave, Loop Cave and Horse Hoof Cave. Huanglong Cave is located near Huanglong Temple and contains different kinds of stalactites and stalagmites. It is the largest travertine cave in China. It is also a natural ice cave with the longest freezing period in China.

** Geological explanation

Fundamentally, the colored ponds in Huanglong were formed by water erosion. In geological terms, this is known as "karst land formation".

Since karst landforms are so common in China, why is the large area of colorful ponds only found in Huanglong?

The water from snow and ice on the high mountains surrounding Huanglong Valley, together with the surface water, filters through moraines and forms an undercurrent, dissolving a great deal of calcium carbonates via the circulation of underground water. The underground water then replenishes the brooks through the mouth of the spring and crannies between rocks. Once on the surface (with the reduced temperature and pressure), carbon dioxide is released from the water. Next, the calcium carbonates in the water crystallize and separate，forming the so-called travertine, which will collect on plant roots or branches. Travertine sedimentation is formed with the twists and turns of water flow. Through tens of thousands of years, travertine dykes ranging from t10 centimeters to 2 meters high were formed along the landforms, producing ponds of different colors and sizes within the dykes.

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