Being such a big country, there is no chance to give an appropriate summary of Chinas geology on this page. So we will try to list some highlights, being far from completeness.
The karst areas of China are outstanding. The caves are spacious, the cave systems are often quite long. China has no extraordinary world records, which may be primarly a matter of lacking research. Still both, the second and third largest underground chambers are located in China. (BTW: the largest chamber of the world is Sarawak Chamber in Good Luck Cave, Malaysia, on the island Borneo)
About 20% of Chinas surface are covered by limestone karst. The most important karst areas are found in the south (Guangxi, Yunnan, Guizhou, Hubei, and Hunan). Especially at the coast of the Chinese Sea, the karst has a typical face: the tower karst. At the coast the towers form steep limestone islands in the Chinese sea. Sichuan in central china is also a very important karst area.
A very special feature are the big loess plains of the Gobi desert in northern China and southern Mongolia. Loess is a layer of dust or fine sand, several tens of meters thick, composed mainly of limestone. This deposit was formed during the ice ages, when enormous glaciers covered the land and pulverized rocks. The fine dust was blown away by hard winds, not slowed down by vegetation on the ice shield and the neighbouring cold tundras. It was then collected by the first vegetation it reached.
The loess now appears as a soft sandstone which can be easily excavated with a shovel. But in contrary to its softness it is very stabile, it does not cave in! For centuries people have dug into this deposit to make houses out of the living rock.