There’s a jungle inside Vietnam’s mammoth cavern. A skyscraper could fit too. Hang Son Doong, or “mountain river cave,” is in a remote part of central Vietnam. Hidden in rugged Phong Nha-Ke Bang National Park near the border with Laos, the cave is part of a network of 150 or so caves, many still not surveyed, in the Annamite Mountains. You can read the full story of the cave explorers expedition here.