A group of "dolines", ancient sink holes, in south China's Guangxi Zhuang Autonomous Region, opened as a tourist attraction on Wednesday.

The doline group, the oldest and largest in the world, is located in Leye County, 460 km from Nanning, capital of the autonomous region. It was formed some 65 million years ago.

"Dashiwei", the largest hole of the group, is 613 meters deep and 420 wide. The virgin forest on the bottom of the doline covers an area of more than 10,000 sq meters, about one and half football grounds. It is inhabited by more than 1,000 varieties of plants, including many rare species, such as blindfish, crabs, shrimp, and flying squirrels.

Dolines, a special geological landscape found in karst regions, were formed by repeated cave-ins of the tops of underground caves. They are mainly seen in China, Mexico and Papua New Guinea.

Hong Zongdao, Party chief of Leye County, said that Guangxi has invested several hundred million yuan in building local infrastructure, improving security and service systems. The doline "museum" is capable of receiving 3,000 tourists daily.

The doline group was not found until 1998 when the Ministry of Land and Resources surveyed in Leye county.

An expedition consisting of experts from nine countries traversed the doline group last year. Zhu Xuewen, the initiator of the exploration, has participated in exploration operations into the dolines in Leye since 1999.

Zhu, also a research fellow with the Institute of Karst and Geology of the Chinese Academy of Geology, hoped that effective measures would be developed to protect the dolines from destruction in the wake of increased human activities.

The world's single biggest doline, Xiaozhai Doline, with a depth of 660 meters and area of 119 million cubic meters, is located in the Chongqing Municipality on the upper reaches of the Yangtze River.

(Xinhua News Agency October 2, 2003)