I slept in the world’s largest cave, discovered by accident in 1990 and so big it has its own jungle, river and WEATHER… and could house a 60-storey skyscraper

As the sun sinks below the horizon, I pitch my tent on the sand.

My fellow campers are busy setting up their beds for the night. I leave my door open, lie down on my sleeping bag and look out over the beauty of our surroundings.

This place in Vietnam is a unique strip of sand, deep in the Phong Nha-Ke Bang National Park – in the colossal cave chamber of Son Doong.

Wandering around here feels like walking through the heart of the earth.

Only 1,000 visitors are allowed each year, in groups of 10. The six-day tour quickly sells out at the only recognized tour operator, Oxalis Adventures.

The cave has been confirmed by Vietnamese officials as the largest in the world and Guinness World Recordswhich in 2012 stated that it is 200 meters high, 150 meters wide and ‘at least’ 6.5 kilometers long.

When the document was recognized, the organization admitted that the cave may have been even larger, as it had not yet been fully explored.

Oxalix adventures is approximately 9 km (5.5 mi) long and offers enough space for a vast jungle, river, weather system and a 60-story skyscraper.

Remarkably, the cave remained sealed for millions of years until it was discovered by chance in 1990.

According to my guide, a local man, Ho Khanh, stumbled upon this underground wonder while looking for shelter from a storm.

The villager was searching for an expensive plant known as agarwood and came to the entrance of a cave under a cliff. But as he got closer, he saw mist blowing from the cave and heard a roaring river.

Nearly twenty years later, the site was shared with caving experts and the first trial tours were held in 2013, followed by the official launch of the Son Doong expedition a year later.

It’s the most surreal campsite I’ve ever seen.

Looking out of my tent, I take a deep breath as the sun casts an enchanting light through the cave.

The distant echoes of dripping water provide a soothing lullaby as I prepare for the night, enveloped by the massive limestone walls that surround me.

In the misty morning, the first rays of sunlight shine through the opening of the cave, reminding us of the dense forest above.

I know now, after the two-day hike here, with climbing over rocks, rope climbing and ladders.

It all started with a minibus dropping us off at the top of a valley at 9am, after which we descended into the jungle.

Water seeps through my boots as we wade through shallow rivers and streams, but they provide the traction needed for the steep climb to the first campsite at Hang En Cave – the first of two caves on this expedition.

As I walked towards the mouth, I felt as if I thought we had reached Son Doong before the scheduled time.

It is the third largest cave in the world, with a ceiling that is 145 meters (475 feet) high at its highest point and the widest part of the passageway is up to 200 meters (656 feet) high, according to Oxaxlis adventures.

The sheer size is impressive, with a spooky atmosphere. The only sound – the chirping of swifts, which could be heard but not seen.

“This cave is named after the birds. They nest here,” our guide said.

There is time for a quick dip in the river while our porters set up the kitchen and the cooks prepare various dishes for dinner.

Then we gain energy for the next day. We walk through the cave, wade through rivers and climb steep slopes.

I realize how long Son Doong has remained hidden until we reach the opening and descend 80 meters (262 feet) underground using ropes.

As we descend, the enormous cave slowly becomes visible and the temperature immediately drops.

After much scrambling and clambering we arrive at the next camping spot, this time in the impressive cave of Son Doong.

It’s the moment we’ve all been waiting for and it feels like we’re entering another world.

The rocky cave is so high that it leaves you speechless, especially when you crane your neck to look at it.

Light pours through the door into the room, highlighting the bright green foliage beyond.

But it’s not enough to warm the sand on the ground, because it feels cold between my toes.

In this deserted environment we are surprised to see that toilets and changing rooms have been set up. This has made for the most comfortable night so far and I am looking forward to sleeping well in this dark cocoon.

The next day we climb the steep walls of the cave, winding through small openings to reach the forest inside.

The cold, still air is of an unparalleled purity and we cherish the faint points of light in the darkness that we share with bats, spiders, fish and scorpions.

But all I see of these cave dwellers is the shadow of bats as they swoop down from the ceiling at dusk or when they are disturbed by the light of our headlamps.

The moment our guide tells us that we don’t have to cross the river anymore is a real pleasure. I immediately stop to put on a pair of dry socks.

As we emerge from the cave, I see the sun once again sinking below the horizon. This time, it is fully in view.

After a few days underground it’s a beautiful moment, but I would trade it for another night in the dark if it meant having to go back to Son Doong.

Laura visited Hang Son Doong with Oxalis Adventure. Visit oxalisadventure.com.