Deep in the jungle of Central Vietnam there is a wonder of the world. A unique ecosystem. A cave. What’s so different about this cave? It’s the largest cave in the world like nothing you’ve ever seen before. It might as well be a Holy Grail for a biologist and cavers. The Hang Son Doong cave (“cave of the mountain river”) located near the Laous-Vietnam border.

This cave of Vietnam is an uncharted territory and next to no one has forged this monstrous cave. In 2009, Cabaret Jonathan Sims was one of the first people to set foot in the cave but deep into the passage and he was stopped short by a forbidding rock-face. In 2010 he was back with caving expert and expedition leader Howard Limbert. He brought more advanced climbing equipment and a commitment to reach the top of the wall. He wanted to know if this cave was larger than the previous cave in Malaysia- the Deer Cave which holds the record for the biggest cave in the world. And for that he needed to get to the Great Wall in Hang Son Doong cave.

The expedition began with a dangerous 328 foot rappel into the first massive cavern.  British caver Howard Limbert had led 12 expeditions to Vietnam’s limestone caves. 2010 year’s expedition into Hang Son Doong cave was especially dangerous because it’s so remote.

“Anybody could fall, twist their ankle, break their ankle, those things can happen” as told by Limbert in National Geographic.

In 2009, Limbert and expedition were only able to explore the first section of the cave but they found areas they estimated to be about 500 ft wide and about 650 ft high. That’s about three times the height of Niagra falls.

Jonathan Sims is one of the four cavers that drew up the rough original survey of Mountain River Cave. He knew the wall that defeated him back in 2009. That was his biggest challenge and it was a dangerous obstacle to overcome. Made of loose Calcite and mud it stands to nearly 50 ft high.

14-passing-great-wall-714The Great Wall of Vietnam

Sims wasn’t expecting anything like that when he first ventured into the cave and yet he was determined that this time would be a success. He won’t fail twice. They could climb this forbidding wall. He was convinced that the enormous cave continued on. They estimated that the wall was about three miles into the cave. From the 328 ft rappel of the entrance, it would take the team half a week to reach the final survey point.

What Limbert’s expedition figured out from the rough draft of the cave was that after the initial drop there was an eleven-hundred-fifty ft scramble that led to the first of two river crossing.  From here the team needed to climb high following the river through the natural valley of the cave then there would be a decent down to a level sandy area into the first of two Dolines (collapsed hole in the cave’s surface).  The Dolines and cave beyond were where Betcher (the expedition’s German Zoologist) hoped to find new life forms and Granger (another caver in the expedition)  to find the secrets to how the cave was formed and then through a narrow section across the larger Doline and into the second camp. So far the final part of the cave surveyed was the last quarter mile before the Great Wall of Vietnam. And from there, it’s into the unknown.

Limbert’s team was all experienced cavers that had been exploring caves since 1990. One thing that was ideal for cave formation was water.

wtaer           The expedition exploring the cave

The Mountain River Cave was filled with normal water, small streams that they had to walk through. The rivers are trapped within walls of non-soluble blocks which hold the water in. But what they found out next, the results were spectacular.

The volume and power of the water helped create these gigantic caves. At a monsoon climate with heavy downpours feeding the many rivers here and the chances of water carving out of the colossal cave were even greater.

So far, the expedition had discovered 62 miles of caves but none as epic as this. They suspected additional factors must have been at work here. The team needed to navigate through the difficult broken terrain to reach the first camp.

They were nearly a third of a mile into the cave with 65 feet to go before reaching a powerful river. This river runs like a main artery through the first part of the cave. It carved this enormous cave and the team would have to navigate it twice. Limbert lead the way.

Once they reached the river they were awed by the sound and sight of the scary powerful rushing water. But they didn’t fall back. They were even more determined to move forward. For that they would have to cross this deep threatening underground river.

They worked hard in drilling and hammering a stable, heavy rock with ropes that would let them pass through it. If the drilling and the rope that embedded into the stone pops then they had to have a buckle. They needed to make it as safe as possible or they would be swept away by the force of the river and into sharp rocks below or unknown areas and be lost. If it floods it could rise and cut off their escape routes. It was a life or death situation.


crew                The team crossing the dangerous river

With the ropes tightly bound from -one end of the river to the other, they crossed it one by one. Gripping it with all their might and trying their hardest to not let their feet give away. Once everybody reached the other side they breathed a sigh of relief. With a great obstacle overcome Granger could now really start to look around to find answers to how the cave became that large.

Granger found out that the answer lies beyond and so Limbert’s team set foot to venture deeper into the monstrous cave. They had food for six days, enough to last till they get to the Great Wall of Vietnam and back. The team being exhausted from that entire venture had set up camp to rest till next day.

The day broke. Morning had arrived and the team continued onward to the Doline. Reaching the Doline wasn’t as tough as crossing the river. And when they got there they broke into grins and stunned at the sight in front of them.

It was a collapsed Doline. A huge wall of the cave had collapsed into the cave and a hole was created letting in sunlight and rain. This in turn gave rise to green. A whole jungle with a different ecosystem from the outside world resided in the cave with its very own climate.

8f71b53b385882854db75f0b32fa_w1024_h731_gi-photo-576173 “Watch out for Dinosaurs” Doline…the collapsed doline

“It’s got to be one of the wonders of the world. It doesn’t happen anywhere else on the planet” said Limbert in absolute awe.

At some point in the cave’s past the river ate away the cave’s roof where the limestone beds are thinner. The river damaged the ceiling rock so much that eventually the roof collapsed.  This collapse is known as Cantilever Failure.

After exploring the jungle and still seeking out how the cave was formed they moved on. Away from the light and again into the darkness.

Limbert yells a word into the cave. The echo that occurs would tell him if he could continue deeper into the cave. Limbert believed that this cave is longer and wider than Deer Cave but he needed to find the highest area to confirm it.

Hope lied beyond The Wall and there was only three days left for the survey but there was an unexpected problem that mounted. To continue their journey they needed a clear visibility. Just as the cave allows light to enter it also allows the clouds and they couldn’t continue with a precise journey if their visibility would come down.  This became a paralyzing setback. They were running out of time and resources. They need to get to the end of the cave. And does the end even have a way out? They couldn’t turn back because they were already more than half way in. They could only find out if they moved forward. Limbert had to make a tough decision.

He sent his two best climbers, Clark and Sweeny, ahead to set the rigging on the treacherous Wall of Vietnam so the rest of the expedition could follow the next day. If they could’t scale it they might not finish the survey and never find out if this was the biggest cave in the world. All of their trails would have been a waste. Could they even scale it successfully?

In 2009, the explorers estimated The Wall to be nearly 50 ft tall. In 2010, when Clark and Sweeny got to the Wall they knew it was much bigger estimating 200 ft. They had the gear for the challenge but the climb was going to be longer and much more dangerous than expected.  This wall could be the mission’s downfall.

15-great-wall-vietnam-714 Sweeny rigging The Wall

Back at the camp the mission was taking a toll even on those who were not battling the wall. Being in mud and dirt they had to keep themselves and everything they had clean. Sand and dirt were getting into their shoes and socks were getting dirty and even their clothes. Walking continuously through river and mud created fungal infection on their feet. And the chance of failure was frustrating. They needed to finish this expedition as soon as possible and get out. Time was running out.

Limbert and the rest of the team waited nervously for news. While the tension was brewing Granger finds out how the cave was created in the first place. He spotted an old fault line on the map of the cave. That explained how the cave was created.

Once a river ran where Mountain River cave exists today. There was a deep vertical crack in the earth’s crust called a fault. Eventually the river water eroded the limestone and went deep underground. Once the water filled the fault and found the exit the river started to erode the rock along the crack and a gigantic cave was formed.

“The reason the caves fall apart is often because they get too wide and the limestone can’t support along that length” Granger explained.

Here the straight jacket of the Geological fault restricts the cave’s width reducing the possible risk of collapse allowing the cave to continue to grow without breaking down in a straight line. This created a never-before-seen gigantic cave.

While Ganger theorized about the cave Limbert needed to know if Sweeny and Clark managed to climb The Wall. Limbert’s walkie-talkie finally rang and he got the news he had been waiting for. His team has reached the top of The Wall. The height or pitch was more than anyone had anticipated.

“I was doubtful if we could do it. I didn’t think it was possible to climb 80 meters of The Wall. But they managed to do it” Limbert sighed with relief as he told his team.

Now the problem is what lay beyond it. Would it be a dead end or would they be able to get out? It all relied on fate and luck. The final hurdle now awaited Limbert and his team. They needed to push-on to meet the other two at the top of The Wall.

It took almost two days for Sweeny and Clark to have gotten up there. How long would it take for the rest of the team? Would they reach safely?

The team finally arrived at The Wall. It towered terrifyingly above them. Limbert was looking at a section that would tell them if this cave was bigger than Deer Cave. And now that section was at the top of The Wall. They had to get up there.

Limbert and his team attacks The Wall, the rest of the crew then followed. Climbing up with all their strength and will. This was no easy task. It was for expert climbers and they were struggling. But alas, he could feel the end reaching. Covered in mud and sweat and exhaustion their finger-tips felt the top of The Wall. Would there be an exit? Will they be able to get out? Or would it be a dead end and they would be doomed to track back with less resources and all of those life threatening hurdles again?

They were answered by wind and light and chirping of birds. It was the end of the cave and there was a way out into the forest. They all breathed a sigh of relief.


Limbert could now measure the cave at the tallest point. Would it be a record breaking find?

“96.4…96.4!” Limbert yells with excitement, “It’s massive!” It was twice the size of Deer Cave! The expedition was happy that they had triumphed. They came over massive obstacles and life threatening situations. Their foot prints would be of the first few people that had conquered Mountain River Cave and came out alive!