The famous Hillary Step - the last great challenge before the top of Mount Everest - has collapsed, potentially making scaling the peak more dangerous.
The near-vertical 12m rocky outcrop on the mountain's southeast ridge was named after Sir Edmund Hillary, who was the first to scale the mountain in 1953.
British mountaineer Tim Mosedale confirmed the Step had gone on Facebook after scaling the mountain.
He said the loss of the Step was "the end of an era".
"It is associated with the history of Everest, and it is a great shame a piece of mountaineering folklore has disappeared," Mr Mosedale said.
Mountaineers said Step may have fallen victim to Nepal's devastating 2015 earthquake.
Back in May 2016, pictures posted by the American Himalayan Foundation appeared to show that the Hillary Step had changed shape.
But thanks to the snowfall, it was hard to tell for sure. This year, with less snow, it was clear the Step had gone.
"It was reported last year, and indeed I climbed it last year, but we weren't sure for certain that 'The Step' had gone because the area was blasted with snow," Mr Mosedale wrote on Facebook.
He concluded: "This year, however, I can report that the chunk of rock named 'The Hillary Step' is definitely not there anymore."
Mr Mosedale, who is due to go back up Everest later this month, said he believed the Step was most likely a victim of Nepal's 2015 earthquake.
"It could well just be gravity, but I would suspect the earthquake was the cause," he said.
Mountaineers claimed the snow-covered slope would be much easier to climb than the notorious rock face, but warned it could create a bottleneck.
That would be a serious worry for those already battling low oxygen and frostbite conditions at the top of the world.
Speaking to the BBC in 2012, British mountaineer Sir Chris Bonington said getting stuck near the Step could be fatal.
"If it's a perfectly fine day, it doesn't really matter too much if you are delayed for say, an hour and a half, two hours on the Hillary Step, which is just short of the summit.
"If the weather is breaking up, that two-and-a-half hour wait can be a matter of life and death."