By Hannah Stevens @Hannahshewans

DELVE into an ancient nest of magnificent caves formed over 400 million years ago

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The National Park was created to protect the world's two largest karst regions with 300 caves and grottoes

Photographer Claudio Sieber ventured into Vietnam’s famed Phong Nha-Ke Bang National Park in Vietnam to explore the intricate network of caves, which is home to the largest cave in the world.

Hang Son Doong cave boasts heights of 200 metres and stretches five kilometres into the mountains, but tourists hoping to visit face fees of up to 4000 US dollars - a price out of Sieber’s reach.

Instead the nomadic photographer spent several days swimming, exploring and documenting several of the other stunning caves, including the natural cathedral housed inside Paradise Cave.

The sprawling region also protects the ecosystem of limestone forest in the Annamite Region in Northern Vietnam

He said: “Depending on the cave it’s either eerie or just overwhelming what nature is able to create.

“There is a big difference between exploring a wet cave and swimming through the darkness and walking on a well prepared passageway.

“In some caves one feels like you’re in an ancient nature museum while in others you’re Indiana Jones with a torch.”

Many areas of the underground web have yet to be fully explored

The national park was named a UNESCO World Heritage Site in 2003 but did not open to the public until 2013.

Hundreds of caves make up the breathtaking site, however serious exploration of the caves was not undertaken until British explorers delved deep into the system in 2003.

The National Park houses the world's largest cave - Hang Son Doong cave

Used to travelling at his own speed, Claudio found the carefully planned expeditions a little strange.

Sieber said: “Tours are a bit too organised for my liking, it gave me kind of a luxury feeling.

The parks name originates from the Phong Nha Cave and the Kè Bàng Cave

“As an easygoing adventurer, I did not even need a third of the provided equipment, porters or food.”

“But that’s subjective, most of our small group were happy to stay within a certain comfort zone.”

For its geological value, the site was listed as a UNESCO World Heritage Site in 2003

Despite his disappointment with the strict schedule, Claudio was entranced by the eerie peace permeating the web of caves.

Hang Son Doong cave was not discovered until 2009 by the British Caving Association

He said: “We hiked up to a small wet cave where we had to swim from the entrance to the exit while bats were flying close above our heads.

Visitors to the park were not permitted until 2013

“It’s a different world, sitting in the cool waters and listening to the drops falling from above.”