Expedition members work within the Miao Room Chamber, China's largest cave chamber by volume, in Ziyun County of southwest China's Guizhou Province, April 14, 2016. In 2014, National Geographic announced Miao Room Chamber, with a volume of some 19.78 million cubic meters, as the world's largest cave chamber. A joint caving expedition code-named "Pearl" by explorers and scientists from China and France kicked off here on April 11. During the 19-day exploration, they will conduct comprehensive investigation on famous caves in Guizhou including the Miao Room Chamber and Shuanghe Cave in Suiyang. (Photo: Xinhua/Ou Dongqu)