Son Doong Cave.
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Visitors will get out of the cave by the “back door”, instead of returning to the same entrance as in the previous exploitation plans. This option is supposed to be optimal, helping to ensure the rescue work if needed and also provides favorable conditions and new experiences for visitors.
During 2017, Oxalis has effectively operated its tours on conquering Son Doong, contributing to meeting the needs of visitors who want to explore the UNESCO-recognised World Natural Heritage Phong Nha - Ke Bang National Park.
This year Son Doong has welcomed 740 visitors, with two routes, including five days/four nights and four days/three-night packages. In particular, the latter was piloted in the three months since last May, with 19 tours serving 188 visitors.
Son Doong Cave is a solutional cave in Phong Nha - Ke Bang National Park, Bo Trach District, Quang Binh Province, Vietnam. As of 2009 it has the largest known cave passage cross-section in the world and is located near the Laos – Vietnam border. Inside is a large, fast-flowing subterranean river. It was formed in Carboniferous/Permian limestone and is believed to be between 2 and 5 million years old.
Son Doong Cave was found by a local man named Ho 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 conducted a survey in Phong Nha - Ke Bang from 10 to 14 April 2009. Their progress was stopped by a large, 60-metre (200 ft) high calcite wall, which was named the Great Wall of Vietnam. It was traversed in 2010 when the group reached the end of the cave passage.
According to the Limberts, the main Sơn Đoòng cave passage is the largest known cave passage in the world by volume. The cave runs for approximately 9 kilometers (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 which has resulted 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 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 800 permits available for the 2017 season, which runs from February to August. After August, heavy rains cause river levels to rise and make the cave largely inaccessible. There is currently only one expedition company with permits to enter the cave for tourism purposes.
