These spectacular images capture the breathtaking beauty of a newly discovered ice chasm beneath the Rocky Mountains.
The enchanting cave, known as the 'Booming Ice Chasm', is renowned for its incredible acoustics, as falling rocks crash and 'boom' when they tumble down the 140m-deep cave.
The chasm is so expansive that climbers find it difficult to communicate because of resounding echos.
Intrepid explorers Adam Walker, Nick Vieira and Christian Stenner have to wait several seconds after each syllable just to communicate in the giant expanse of ice.
The cave is known as a 'cold-trap cave' where cool winter air settles into the depth and is never able to escape.
As melting snow and rainwater trickle down the cave entrance it's transformed into an amazing natural frozen water slide.
The spectacular snaps were captured by Belgian photographer Francois-Xavier De Ruydts, 30, on an exploration to the Crow's Nest Pass area of Alberta, Canada, in July.
Francois, who lives in Vancouver, Canada, said: "It's particularly hard to get around when inside the cage - traction devices called crampons are mandatory.
"It can be fatal if you slip as you slide all the way to the bottom crashing into the wall at a frightening speed.
"The danger in the cave is that once you are down there, if you have a problem, the only way back is to go all the way through where you came from.
"Few injuries in caves are fatal but it can take days to bring an injured person back to the surface and many die of exhaustion and hypothermia in the process.
"The additional danger in this cave is the ice - it makes it much harder to get around and much colder.
"Several passages which feed off this cave have yet to be explored. The incredible ice fall that flows from the thin passage has never been climbed and no one knows what lays beyond it.
"I have never seen anything like this before. It is a truly unique sight and there are very few caves like this, particularly as big as this one."