Hidden in the depths of the Vietnamese jungle lies The Hang Son Doong, part of a network of over 150 caves.
Discovered by British cavers in 2009, the cave passage in Phong Nha-Ke Bang National Park was originally thought to be a modest 150 metres long and 200 feet high.
But these remarkable images - taken during two further expeditions of the caves - show the previously undiscovered depths of the magnificent cave passage, now the largest in the world.
At a mammoth 2.5 miles long, 330ft wide and almost 800ft high, Hang Son Doong also known as Mountain River Cave, is as high as 25 double decker buses.
And as shown in these amazing images taken by photographer Carsten Peter, there is even a jungle concealed deep inside the cave.
Carsten from Munich, Germany, took the images in 2010 when he joined British and German cavers during further expeditions of the site.
The purpose of the expedition was to make a complete exploration of Hang Son Doong and create a photographic record of the cave.
Cartsen, 52 said he spent up to two weeks at a time deep inside the caves, where he slept with just a sleeping bag and spent his time exploring and photographing the secret underground world.
He said: ‘We discovered new parts of the cave, it's a huge area so to find them and access them is very difficult.
‘Photographing caves of this size is a challenge, it needs a lot of preparation.
‘But it's a great feeling to photograph a newly discovered cave, for me I see the cave for the first time when I see the photographs.
‘I love to explore, I have been in some great caves in my lifetime and this is one of the most magnificent.
‘I've been a photographer and explorer for the last 35 years and I've visited so many caves, I've lost count.
‘But this is by far one of the most unique and unusual caves I have ever seen.
‘To see a cave so large it has a forest inside is superb - it was overwhelming.’