With the eerie green glow inside the mystical, echoing cavern, Son Doong Cave looks like it could be on the edge of the world.

At more than 200m high, 150m wide and 8.5 km long, Son Doong cave in the Phong Nha Ke Bang National Park - large enough to fit a 40-storey skyscraper - is so massive that it has its own climate, and clouds even form inside it.

The cave was formed between 2 and 5 million years ago. It is classified as the largest in the world by the British Cave Research Association.

Zihlmann had gone on a special photographic tour of the cave and his stunning snaps were post on Dailymail.

Urs Zihlmann said to Dailymail that he was very lucly to be able to go on a guided tour of the cave.

"As we approached the entrance, clouds were rising from the cave into the surrounding forest - we had to descend 262ft down a steep wall, using harnesses and ropes" he said.

"Standing on the slippery ground in a huge, dark chamber, you begin to realise how amazing it is. You feel very small as a human being in this enormous, underground paradise - it has such an unearthly beauty", added the Australian photographer.

Tours of the cave are limited to 450 visitors each year to ensure sustainable future for the crumbling cave.

By Nhu Y
(Source: Dailymail)