A newly-launched expedition inside Thoong Valley in the heart of Phong Nha-Ke Bang National Park allows visitors to go kayaking through emerald waters and admire crystal stalactites.
Source: VNExpress International,
https://e.vnexpress.net/photo/places/crystal-stalactites-emerald-lake-hidden-inside-phong-nha-ke-bang-valley-4543395.html
