The entrance to Son Doong, meaning “cave of the mountain river,” was first discovered in 1991 by Hồ Khanh, a local logger. In 2009, a team of scientists and explorers, having heard tale of Hồ Khanh’s fabled discovery, contacted him and requested his help to find the cave. It took several months, but he eventually retraced his way back through the remote jungle to once again find the dark, foreboding maw in the earth.
He and the team of scientists, using proper caving systems and techniques, pushed exploration into the cave.
All were utterly astonished by what they saw.
The cave, estimated to be between two and five million years old, is believed to be the largest cave passage in the world. It’s more than three miles long, with numerous chambers large enough to hold an entire city block of New York skyscrapers. Being the world’s largest cave, Son Doong contains many appropriately gargantuan formations, including the 200-foot “Hand of the Dog,” which might be the world’s largest stalagmite, as well as baseball-sized “cave pearls,” a type of speleothem that’s typically much smaller.
Son Doong is also distinguished by two large dolines, areas where the cave roof collapsed, that let in light and created conditions for dense prehistoric flora to grow in the middle of the cave.
Formed of Carboniferous/Permian limestone, the main Sơn Đoòng cave passage is the largest known cave passage in the world by volume – 38.4×106 cubic metres (1.36×109 cu ft), according to Howard Limbert. It is more than 5 kilometres (3.1 mi) long, 200 metres (660 ft) high and 150 metres (490 ft) wide. Its cross-section is believed to be twice that of the next largest passage, in Deer Cave, Malaysia. The cave runs for approximately 9 kilometres (5.6 mi) and is punctuated by 2 large dolines, which are areas where the ceiling of the cave has collapsed. The dolines allow sunlight to enter sections of the cave, resulting in the growth of trees as well as other vegetation.
The cave contains some of the tallest known stalagmites in the world, which are up to 70 m tall. Behind the Great Wall of Vietnam were found cave pearls the size of baseballs, an abnormally large size.
In 2013, Oxalis Adventures became the first (and only) licensed company to run tours into the caves. For $3,000, tourists were granted a six-day trip deep into the cave's interior. In 2015, Oxalis plans to offer eight trips a month into the cave, lead by BCRA experts who were all part of the original expedition into the cave.