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.

Vietnam’s Son Doong cave, the largest in the world, could hold a 40-story skyscraper inside. The pristine ecosystem has its own river and jungle. Despite its size, Son Doong wasn’t discovered until 1991. It was lost again for nearly two decades and was fully explored for the first time in 2009. (Photo by Jason Speth/HuffPost)

These breathtaking images capture the hidden depths of one of the worlds largest caves, which is so big its home to a beach, a river and a jungle. At more than 130m high, and 150m across, the imposing cave is so big as high as the London Eye and wider than one-and-a-half football pitches. Here: The campers set up inside the cave on the beach. (Photo by Lars Krux/Caters News)

Floating on clear deep water and reflections near the cave entrance. Visitors can either bring their own kayaks or rent boats from the local community to paddle deep inside the cave and marvel at its wonders on March 2015 at Tham Khoun Ex, Laos. Tham Khoun Xe, commonly known as the Xe Bang Fai River Cave, in Laos, has over 15km of passages filled with awe-inspiring views and wide expanses of water. Photographer, John Spies, 59, captured scenes from the entrances of the huge underground river passages, intricate cave formations and views from a passage high above the water. The cave is formed by the Xe Bang Fai river, a major tributary of the Mekong and in the dry season can be traversed using inflatable kayaks. (Photo by John Spies/Barcroft Media/ABACAPress)

Slovenian photographer Peter Gedei started caving 25 years ago and has carried a camera with him on every trip getting stunning pictures from his travels, capturing the ice formations, tight chambers and beautiful halls. Photo: The Ice Cave in Postojna, Slovenia. (Photo by Peter Gedei/Caters News)

Ra Paulette is an American cave sculptor based in New Mexico who digs into hillsides to sculpt elaborate artistic spaces inside mountains. Reviewer Martha Mendoza in the Los Angeles Times described the caves he created as shrines, as hallowed places, a “sanctuary for prayer and meditation” while others describe the caves as works of art. The caves are finished with “scallops, molded curves, smooth ledges, inlaid stones, narrow pods and crusty ledges”. His caves attract visitors worldwide.

These otherworldly images give a rare glimpse inside caves barely ever seen by the human eye. With its peculiar pools of water and strange colored sediments, the bizarre looking tunnels of the Shakuranskaya cave could be a set straight out of a science fiction film. Found in the disputed region of Abkhazia, around 75 miles outside of Sochi, Russia, it is rumored the incredible underground chambers were formed after a huge earthquake struck the area in 1892. After causing part of a nearby mountain to collapse into the Amtkel River, it is thought the dam-like affect has created a series of interconnecting underground tunnels. Here: a large pool of water inside one of the tunnels. (Photo by Vladimir Mulde/Caters News)