Geologists have discovered a group of 19 sinkholes in the city of Baise in south China's Guangxi Zhuang Autonomous Region – the largest cluster south of the Tropic of Cancer. /VCG Photo

The sinkholes feature lush vegetation, valleys and waterfalls. Scientists are interested in the different geological formations inside these holes as well as the many plant species at the bottom of the structures. /VCG Photo

The cluster has a volume of over 1 million cubic meters and is part of a group of sinkholes in an area of about 100 square kilometers. /VCG Photo