The Karst topography in Guilin is one of the largest in the world and thanks to the receding water from hundreds of millions of years ago, the gulf in Guilin bared hills made from limestone and dolomite rocks. As the hills protruded in the newly revealed landscape, rain, wind, and countless rivers develop the unique contours of the hills and the magnificent structures in the caves. All of these took 70 million years for nature to pull off.
As acidic water slowly eats the bedrock by flowing to the fractures on the ground, these cracks became wider and allow more water to pass through them accelerating the formation of underground drainage creating caves and underground rivers. The Guilin Karst landscape is a classic example of a large-scale bedrock dissolution process, dissolving more bedrock than it eventually left out. This made the towering Karst hills possible.
In fact, the sharp, slender slopes made the Guilin site very unique from other Karst landscapes of the world. This explains the extensive underground structures – a lot of water was channeled from the hills to the ground creating enormous cave complexes. The scale of the hills and the huge number of interconnected caves and rivers made this area a wonderful place to just be amazed at the natural sites on your every turn.
According to the Internet