Hang Son Doong in Vietnam is the largest cave on Earth.
Located in Phong Nha-Ke Bang National Park near the border of Vietnam and Laos,this behemoth is over approximately 5.6 miles long and contains its own large, flowing river.
The huge cave – large enough to fit a 40-storey skyscraper – is so massive that it has its own climate, and clouds even form inside it.
Not only Hang Son Doong is one of the most incredible natural wonders of the world — and the tale of its discovery is just as fascinating.
In 1991, Ho Khanh, a local Vietnamese man who was out hunting in the park., discovered the entrance to a cave, but the descent into the opening was steep—dropping more than 200 feet—and Khanh was unable to enter.
Around the same time,Ho Khanh mentioned his find to Howard and Deb Limbert, two caving experts with the British Cave Research Association, but admitted that he had now forgotten where it was.
Howard and Deb urged Ho Khanh to try and find it again. For the next two decades their search turned up nothing.
However things were to suddenly change, and in 2008 while on another hunting mission Ho Khanh found himself in a section of the jungle he recalled to be near the entrance he found all those years ago. He managed to find it, and carefully retraced his steps back to Phong Nha village to report his discovery to Howard and Deb.
The monsoon season soon kicked in, and the exploration would have to wait until the following year.
In 2009 Ho Khanh returned, this time with the aid of the BCRA. They began their exploration of the cave, which led them to a giant wall that hindered any further progress.
In 2010 they managed to scale the wall, which they called the “Great Wall Of Vietnam”, and find the other exit to the cave.
At this point they realised that the cave was the biggest ever discovered. Named Hang Son Doong, meaning “Mountain River Cave” in Vietnamese.
In 2013, Oxalis Adventures became the first (and only) licensed company to run tours into the caves.
Only 450 visitors are allowed to tour the cave each year,Oxalis aim to ensure a sustainable future for the crumbling cave.
For $3,000, tourists were granted a six-day trip deep into the cave’s interior.
The lucky people who have entered Hang Son Doong so far, like Swiss photographer Urs Zihlmann, have emerged with some amazing photos.
Explorers climb through the huge, dark chamber, which is said to be extremely slippery. Zihlmann described being inside as ‘unearthly’.
On tours, visitors rappel 80 meters to enter Hang Son Doong.
On their first night inside the cave, visitors camp near Hand of Dog, a humongous stalagmite that looks like a dog’s paw.
Fields of algae from ancient pools blanket parts of the cave’s interior.
The roof of the cave collapsed centuries ago, allowing a lush jungle to take root. Monkeys and flying foxes live in what explorers named the Garden of Edam.
With the eerie green glow inside the mystical, echoing cavern, the cave looks like it could be on the edge of the world.
An explorer looks round at the spectacular cave, which takes a half day’s trek to reach, through stunning jungle peppered with butterflies.
Hang Son Doong is a jackpot of rare cave pearls. The pearls form over hundreds of years as water drips down, dries up and leaves layers of calcite crystals on grains of sand.
Scientists have discovered never-before-seen plant species around Hang Son Doong’s waterfalls. Oh, and there’s a whole river in there, too.