Son doong cave is a cave in Phong Nha-Kẻ Bàng National Park, Bố Trạch district, Quảng Bình Province, Vietnam. Currently the biggest known cave in the world, the cave is located near the Laos-Vietnam border. Inside is a large, fast-flowing underground river.
In early August 2013, the first tourist group explored the cave on a guided tour at a cost of US$3,000 each. The group had six members from Australia, Norway, Russia and USA and spent 7 days and 6 nights for the tour. Next exploration trips will be arranged.

Balal, who killed Iranian youth Abdolah Hosseinzadeh in a street fight with a knife in 2007, is brought to the gallows during his execution ceremony in the northern city of Nowshahr on April 15, 2014. The mother of Abdolah Hosseinzadeh spared the life of the her son's convicted murderer, with an emotional slap in the face as he awaited execution prior to removing the noose around his neck. (Photo by Araash Khamooshi/AFP Photo/ISNA)

A plane drops water to put out the fire broke out yesterday in a grassy area in Kizilcahamam district of Ankara and spread to a forest area in Gerede district of Bolu as firefighters, Turkish General Directorate of Forestry teams and officers continue their extinguishing and cooling efforts in the forest fire that is under control on August 22, 2024 in Bolu, Turkiye. (Photo by Emin Sansar/Anadolu via Getty Images)

An Iraqi man comforts his 4-year-old son at a regroupment center for POWs of the 101st Airborne Division near An Najaf, Iraq, March 31, 2003. The man was seized in An Najaf with his son and the U.S. military did not want to separate them. (Photo by Jean-Marc Bouju/Associated Press)

An aerial view of Lake Salt as teams conduct salt extraction works at lake which is a significant portion of Turkiye's salt need is met in Ankara, Turkiye on August 11, 2022. Salt extraction works lasts for about 3 months and continues with the recession of the waters in Lake Salt. The salt extracted from the lake, where salt is produced with a purity of 99 percent, is sent to more than 60 countries. (Photo by Emin Sansar/Anadolu Agency via Getty Images)

A woman and her son hold firecrackers during Diwali, the Hindu festival of lights, in Mumbai, India, November 4, 2021. (Photo by Francis Mascarenhas/Reuters)

A vendor sleeps as his son waits for customers at their roadside vegetable shop in New Delhi, February 12, 2019. (Photo by Adnan Abidi/Reuters)