It's an adventure that demands explorers spend their time in the cold, wet and dark.
But for those who persevere, the results are certainly worth it.
A French-Swiss team have made it their mission to explore a huge network of chambers and sinkholes beneath the Nakanai Mountains of New Britain, in Papua New Guinea.
And for those who thought it was just the lush mountains and forest of the country that were beautiful, think again.
The group's latest expedition into the stunning terrain were captured by French photographer Philippe Bence, 43, who described it as an 'incredible and unforgettable adventure'.