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.

Take a walk on the wild side around some of the most down right dangerous places in the world - and all without leaving your desk, courtesy of Google Street View. Since 2007, Google's amazing technology has given people the chance to visit the Eiffel Tower, peer out over San Francisco's Golden Gate Bridge or walk along a beach in the Bahamas. But as well as mapping the tourist-friendly hotspots, Google also ventured into places you really wouldn't want to find yourself. Here is a collection of some the most notorious areas captured by the infamous roaming camera cars from around the UK and the world.

Festival-goers take a bath in a mud pool during the 20th Boryeong Mud Festival on Daecheon beach in Boryeong City, some 190 kilometers west of Seoul, South Korea, 22 July 2017. Tourists flock to the area to experience the beneficial properties of the Boryeong mud, as well as for a variety of entertainment events. The festival runs from 21 until 30 July. (Photo by Jeon Heon-Kyun/EPA/EFE)

A woman controls a ball on Ipanema beach in Rio de Janeiro, Brazil, April 14, 2016. As hundreds of thousands of tourists begin descending on Rio de Janeiro for the Olympics that start August 5, the headlines have focused on the street violence, the Zika virus, the water pollution and the rush to finish venues and transport. But Rio, known by Brazilians as the “Marvelous City”, glistens despite it all. The beach is a way of life here. (Photo by Nacho Doce/Reuters)

Mount Agung's eruption is seen next to a Balinese temple at Kubu sub-district in Karangasem Regency on Indonesia's resort island of Bali on November 26, 2017. Indonesia authorities raised the alert for the rumbling volcano to highest level on Monday and closed the international airport on tourist island of Bali stranding thousands of travelers. (Photo by Sonny Tumbelaka/AFP Photo)

Performers dressed as Pikachu, a character from Pokemon series game titles, march during the Pikachu Outbreak event hosted by The Pokemon Co. on August 9, 2017 in Yokohama, Kanagawa, Japan. A total of 1, 500 Pikachus appear at the city's landmarks in the Minato Mirai area aiming to attract visitors and tourists to the city. The event will be held through until August 15. (Photo by Tomohiro Ohsumi/Getty Images)

A child looks up to his partner as she stands above the crowd with the support of an elaborate rig of hidden metal rods, during the Bun Festival parade at Cheung Chau island in Hong Kong on May 22, 2018. Thousands of local residents and tourists flocked to an outlying island in Hong Kong to celebrate a local bun festival on Tuesday despite the recording-breaking heat. (Photo by Bobby Yip/Reuters)

Performers dressed as Pikachu, a character from Pokemon series game titles, march during the Pikachu Outbreak event hosted by The Pokemon Co. on August 10, 2018 in Yokohama, Kanagawa, Japan. A total of 1, 500 Pikachus appear at the city's landmarks in the Minato Mirai area aiming to attract visitors and tourists to the city. The event will be held through until August 16. (Photo by Tomohiro Ohsumi/Getty Images)