Photo taken on June 18, 2016 shows the most famous cave Dong Thien Cung at Ha Long Bay in Quang Ninh province, Vietnam. Ha Long Bay, comprising some 1,600 islands and islets forming a spectacular seascape of limestone pillars, was recognized as a UNESCO World Heritage Site, and was named as the world's new wonder of nature in 2011.(Xinhua/Yan Jianhua)