Sơn Đoòng cave is the world's largest natural cave, in Phong Nha-Kẻ Bàng National Park, Bố Trạch District, Quảng Bình Province, Vietnam. Located near the Laos–Vietnam border, Hang Sơn Đoòng has an internal, fast-flowing subterranean river and the largest cross-section of any cave, worldwide, as of 2009, believed to be twice that of the next largest passage. It is the largest known cave passage in the world by volume. Its name, Hang Sơn Đoòng, is variously translated from Vietnamese as 'cave of the mountain river' or 'cave of mountains behind Đoòng '. As a solutional cave, it was formed in soluble limestone and is believed to be between 2 and 5 million years old.
Discovery
The entrance to Hang Sơn Đoòng was found in 1991 by a local man named Hồ Khanh, while searching for aloe, a valuable timber. The whistling sound of wind and the roar of a rushing stream issuing from the cave, heard through the entrance, as well as the steep descent, discouraged Hồ Khanh from entering the cave. Only in 2009 did the cave become internationally known after a group of cavers from the British Cave Research Association conducted a survey in Phong Nha-Kẻ Bàng from 10 to 14 April 2009. Their progress was stopped by a large, high flowstone-coated wall, which was named the Great Wall of Vietnam. It was traversed in 2010 when the group reached the end of the cave passage.
Description
Formed in Carboniferous/Permian limestone, the main Sơn Đoòng cave passage is the largest known cave passage in the world by volume –, according to Howard Limbert. It is more than long, high and wide. Its cross-section is believed to be twice that of the next largest passage, in Deer Cave, Malaysia. The cave runs for approximately 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. By mid-2019, it became clear that the cave is connected by its underground river with a nearby cave called Hang Thung. This increases the effective volume of the cave by more than 1.6 million cubic metres. 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. The scale of the site’s interior is so massive it could fit an entire New York block inside, including skyscrapers, or have a Boeing 747 comfortably fly through without its wings being in any danger.
Tourist activities
In early August 2013, the first tourist group explored the cave on a guided tour at a cost of US$3,000 each. Permits are required to access the cave and are made available on a limited basis, with 1000 permits available for the 2019 and 2020 season, which runs from February to August. After August, heavy rains cause river levels to rise and make the cave largely inaccessible. only Oxalis Adventure Tours have permission to enter the cave for tourism purposes.
Development plans
Plans are being considered to build a cable car through the cave. The proposed system would be long, and cost between $112 and $211 million. The plans are opposed by environmentalists.
Alan Walker released a music video, Alone Pt. II, on December 27, 2019, depicting a young archaeologist on a quest to discover a place of mystery and wonder. After uncovering a hidden secret in a painting, she finds Quang Binh to be just the destination, mesmerized at the marvels of Sơn Đoòng.
