
A tourist visits the Kong Lor Cave in Khammouane Province, Laos, April 9, 2017. The Kong Lor Cave is a karst limestone cave in the Phu Hin Bun National Park in Khammouane. (Xinhua/Liu Ailun)

A tourist visits the Kong Lor Cave in Khammouane Province, Laos, April 9, 2017. The Kong Lor Cave is a karst limestone cave in the Phu Hin Bun National Park in Khammouane. (Xinhua/Liu Ailun)