Hang Sơn Đoòng
|Sơn Đoòng Cave|
|Sơn Đoòng Cave|
View approaching the second doline
|Location||Quảng Bình Province, Vietnam|
|Depth||max. 150 metres (490 ft)|
|Length||approx. 9 kilometres (5.6 mi)|
|Discovery||1991 [AD] by Hồ Khanh|
|Cave survey||2009, British/Vietnamese|
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.
Hang Sơn Đoòng was found by a local man named Hồ Khanh in 1991. The whistling sound of wind and roar of a rushing stream in the cave heard through the entrance as well as the steep descent prevented the local people from entering the cave.
Only in 2009 did the cave become internationally known after a group of cavers from the British Cave Research Association, led by Howard Limbert, conducted a survey in Phong Nha-Kẻ Bàng from 10 to 14 April 2009. Their progress was stopped by a large, 60-metre (200 ft) 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.
Formed in 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.
By mid 2019, it's been revealed that the cave has connection by it's underwater river, with a near cave called "Hang Thung". With that reavel, the cave add to its volume 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.
Son Doong cave doline
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. As of 2017[update] only Oxalis Adventure Tours have permission to enter the cave for tourism purposes.
Plans are being considered to build a cable car through the cave. The proposed system would be 10.5 kilometres (6.5 mi) long, and cost between $112 and $211 million. The plans are opposed by environmentalists.
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- Guinness World Records 2013, Page 032. ISBN 9781904994879
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- Jenkins, Mark (January 2011). "Conquering an Infinite Cave". National Geographic. Retrieved 28 July 2018.
- "World's largest grotto unveiled in Vietnam". Archived from the original on 2009-04-27.
- "Britons claim to find world's largest cave". The Daily Telegraph. London. 30 April 2009.
- Son Doong Cave. "Son Doong cave, Hang Son Doong – Map".
- https://edition.cnn.com/travel/article/son-doong-cave-vietnam-expedition/index.html. Missing or empty
- "Vietnam Cave". National Geographic. July 2011. Retrieved 16 January 2017.
- Arkell, Harriet (25 September 2013). "Five miles long, and with its own rivers and jungle: The world's largest cave is open for tours... you just have to trek for a day and a half and then abseil down a cliff to get there". Daily Mail. London. Retrieved 16 January 2017.
- "First foreign tourist group explores Son Doong Cave". Foxnews. 2018-08-30. Retrieved 2013-08-08.
- "Son Doong Cave tours increase in popularity". 2015-01-15. Retrieved 2015-01-16.
- Letter 1213/UBND-VX, 2016-08-03, Government of Quang Binh Province.
- "Son Doong Cave cable car raises controversy". Vietnam.com. Retrieved 2017-01-16.
|Wikimedia Commons has media related to Son Doong Cave.|
- "Vietnam's Mammoth Cavern". Retrieved 2010-12-21. National Geographic pictorial of Hang Sơn Đoòng
- "American Film Crew's Backstage Inside Son Doong". Retrieved 2015-05-18. Saigon-online-SonDoong-cave
- Strutner, Suzy (September 7, 2013). "World's Largest Cave, Son Doong, Prepping For First Public Tours" (includes video). The Huffington Post. Retrieved September 11, 2013.
- Chùm ảnh khám phá hang động đẹp và lớn nhất thế giới(includes images) Quảng Bình Province (in Vietnamese)
- "In pictures: Inside Hang Son Doong, the world's largest caves in Vietnam". Retrieved 2014-06-20. The Telegraph Online
- "Hang Son Doong" (video on Vimeo). Retrieved March 17, 2015.
- "National Geographic Video March 19, 2015".