The spectacular Han Son Doong cave in Vietnam is so gigantic it could fit a 40-storey skyscraper within its walls
Tours are limited to 450 visitors each year in a bid to create a sustainable future for its vast caverns and plant-life
These stunning snaps were taken by photographer Urs Zihlmann, during a five-day trip to Ke Bang National Park
These incredible snaps giving a glimpse inside the world's largest cave will take your breath away.
With the eerie green glow inside the mystical, echoing cavern, Vietnam's Han Son Doong cave looks like it could be on the edge of the world.
The huge cave - large enough to fit a 40-storey skyscraper - is so massive that it has its own climate, and clouds even form inside it.
These incredible snaps give a glimpse inside the world's largest cave, Vietnam's Han Son Doong, and will take your breath away
With the eerie green glow inside the mystical, echoing cavern, the cave looks like it could be on the edge of the world. Pictured are tents set up for the night
An explorer looks round at the spectacular cave, which takes a half day's trek to reach, through stunning jungle peppered with butterflies
It's not a trip for the faint-hearted - it takes a half day trek through a stunning jungle peppered with butterflies and a journey through knee deep rivers to finally get to the entrance of the colossal cave.
Adventurous explorers must also pass through the third largest cave in the world, Hang Ev cave - used as a location for the Peter Pan blockbuster.