An underground river deep inside Guanyin Cave has become an attraction. [Photo provided to China Daily]

The scarcity of sinkholes means the well-preserved Hanzhong sinkholes are not only of scientific importance, they are also a resource that can be exploited to boost the local economy－the nearby towns are still poor and tourism might help local residents to improve their livelihoods.

French cave explorer Jean Poutasi who inspected one of the sinkholes in Ningqiang county reportedly called it "the world's most beautiful sinkhole".

However, Li Yichao, a senior engineer at the Shaanxi Geological Investigation Institute, said the government should be careful not to overexploit them.

"It takes water, sand, and wind at least half a million years to form these karst geological landscapes, yet the soft touch of a finger could destroy a piece of stalactite within seconds," he said.

Therefore, he proposes protecting the Hanzhong sinkholes by allowing access to only some of the sinkholes and limiting the number of visitors.