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.

Runner-up; Hon Yen marine ecosystem. Phu Yen, Vietnam. Every year between May and August, the coral of this rich and diverse ecosystem becomes exposed at low tide. (Photo by Truong Hoai Vu/Royal Society of Biology Photography Competition)

Vietnam's Khuat Phuong Anh (R) celebrates winning the women's 800m final during the 31st Southeast Asian Games (SEA Games) at My Dinh National Stadium in Hanoi on May 16, 2022. (Photo by Navesh Chitrakar/Reuters)

In this Tuesday, June 23, 2015, photo, an Israeli vendor waits for clients at the southern Israeli town of Sderot, next to the Israel-Gaza border. A year after the Gaza war, the community in southern Israel, long battered by rockets from the Hamas-run territory next door, has slowly recovered and is even seeing a quiet boom. (Photo by Oded Balilty/AP Photo)

Vendors selling candied haws wait for customers at the Harbin Ice and Snow Festival in Harbin, China, January 4, 2016. The festival is open from Jan. 5 till Feb. 5, 2016, and is aimed at attracting both foreign and local visitors to experience the beauty of the ice and snow. (Photo by Wang Zhao/AFP Photo)

Ratana Das, 40, a female vendor, carries sacks full of clothes at a second-hand clothing market early morning in Kolkata, India, March 10, 2016. Das said she was born and brought up in Kolkata and feels proud being a resident of the city that gives her he opportunity to be financially independent. (Photo by Rupak De Chowdhuri/Reuters)

Children of a vendor pose with demon-masks to be hung outside homes believed to ward off negative energy during a government-imposed nationwide lockdown as a preventive measure against the COVID-19 coronavirus, at a roadside stall in Hyderabad, on April 18, 2020. (Photo by Noah Seelam/AFP Photo)

A picture taken with a drone shows a huge work of art created with various flowers and flowering plants in Jacobsdorf, Germany, 29 July 2024. Artist Michael Uy has transformed a piece of fallow land into an insect paradise for bees, bumblebees and butterflies. Using plants, the artist has planted and sown oversized images in the shape of a shell and a winding path of life on a large meadow in Jacobsdorf. (Photo by Hannibal Hanschke/EPA/EFE)