The Hang Son Doong Cave is located in Phong Nha-Ke Bang National Park, Vietnam and broke the record for worlds biggest cave. This massive cave is also known as "cave of the mountain river," and has it's own jungle, river and lakes.

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Hang Son Doong was discovered in 1991 by a local Vietnamese logger named Ho Khanh when he stumbled upon the cave to find cover from a storm. Khanh describes hearing a whistling sound of wind while out on his walk which is what led him to the discovery of the the largest cave in the world. After he returned home he sought out to find the cave again, and finally re-discovered the giant cavern in 2009 with the help the British Cave Research Association.

Researchers surveyed the cave using laser measuring devices. The cave runs for approximately 5.6 miles and in some areas measures more than 460-by-460 feet (140-by-140 meters). Two large sections of the cave, called Dolines, are collapsed. The sunlight they have allowed in the cave has resulted in the growth of lush rainforest. A river runs through the entire cave. It's current eerily rushes into the darkness and can be heard echoing throughout the whole cave system.

The Son Doong cave passage is the largest known cave passage in the world by volume – 38.4×106 cubic metres (1.36×109 cu ft). It is more than 5 kilometres (3.1 mi) long, 200 metres (660 ft) high and 150 metres (490 ft) wide. Research claims that the cave was evolved from limestone eroding over millions of years.

Hang Son Doong is over three times the height of Niagara Falls and can even swallow a 40 story skyscraper. Inside the cave are some of the largest known stalagmites in the world, measuring up to 80 meters (265 ft) long.

The giant cathedral-like cave is a playground for scientists, estimated to be between 400-450 million years old, and full of mysteries from pre-historic times. The rainforest in Son Doong's cave floor is teeming with rare species of insects, and birds like the chestnut-necklaced partridge. Even flying-foxes have been spotted. New species of butterflies, lizards, snakes, bats, and monkeys survive in the caves lush vegetation. Researchers have found that most of the life thriving within Son Doong were albino and living without sight.

Hang Son Doong is now open to the public by a company called Oxalis and they offer a six day trip for visitors. It has only been open since 2013 and tours sell out extremely fast, creating two year long waitlists. In order to explore Son Doong Cave you must hike for a day and a half through dense jungle and then rope down a 260ft wall.

British tourist Simon Dunne was one of the first visitors to the cave. He describes the silence and darkness in the cave as 'deafening'. He added, 'Places that seem a 20 minute walk away take two hours to reach. The darkness really confuses your sense of depth, especially when you're given a rare glimpse of light.'

The brave and lucky explorers who have seen the depths of the worlds largest cave, have returned with images that are literally breathtaking. See how it's gigantic stalagmite and stalactite formations make people appear as tiny dots in the photos.