An enormous limestone cave in Vietnam is the subject of a jaw-dropping new video that uses aerial drones to show its immense scale and beauty. Hang Son Doong is the world's largest cave, featuring a river and huge "skylights" that have allowed trees and wildlife to flourish within it.
American photographer Ryan Deboodt says he filmed Hang Son Doong on his third visit to the cave. He edited his film down from some three hours' worth of footage.
Although it was first shaped millions of years ago, Hang Son Doong wasn't formally discovered until 1991. A team led by British caver Howard Limbert explored the cave more fully in 2009 and has continued to survey it in recent years.
We got in touch with Deboodt and asked how he first came to explore the Hang Son Doong. He replied:
"I first learned of the cave from the article in National Geographic when it was first explored. As chance would have it I was relocating to Vietnam at that same time which led me to start exploring the caves around Phong Nha Ke Bang National Park and finally making it into Hang Son Doong for the first time August of 2013."
In terms of size, the cave's volume is measured at 38.5 million cubic meters. One large passage extends for some 3 miles and is "over 200m (656 feet) high and in places over 175m (574 feet) wide," Limbert writes at the website Vietnam Caves. He adds, "This is the largest known passage in the world as yet discovered."
Large sections of the cave's ceiling collapsed long ago, letting sunlight stream in and creating pristine jungle areas that give two portions of the cave a Land of the Lost look. One of them is nicknamed "Watch out for dinosaurs," and the other is called "Garden of Edam."
Those large skylights are called dolines. In Hang Son Doong, the two largest ones are each more than a mile from the cave's entrance, meaning visitors must climb and hike through darkness to reach them.
Deboodt is a native of Nebraska who's currently based in Beijing. He says he has other plans to photograph caves in China and Vietnam.
For his next project, Deboodt says, he's working on "a long term timelapse documenting the flooding of the caves in Phong Nha Ke Bang."