The BBC is retracing the footsteps of the 1953 British Everest expedition as they made their way up to base camp in preparation for the first successful assault on the mountain's summit. BBC correspondent Jane Hughes, now at base camp, is keeping a diary of her journey.
Day 16:Khumbu Icefall
There's one view from our camp site that is more terrifyingly compelling than any other - the view of the Khumbu Icefall, gleaming white and turquoise in the morning sunlight.
Khumbu Icefall: One false move can spell doom for a climber
It's the first obstacle a climber must overcome in his or her journey up Everest, and it's legendary for its difficulties and risks.
This morning, long before the rest of us were awake, our colleague Tom Heap and our group leader Tim set off up the icefall, to film it and experience it for themselves.
It would still have been dark as they arrived at the edge of the great broken-up expanse of ice.
The earlier the safer is the rule with the icefall - as soon as the sun starts warming it, the vast crevasses that cut across it, and the crazily teetering blocks of ice, begin to melt, and become more dangerous.
A climber and photographer who is camping alongside us, Dirk Troyat, descended from it the day before, and was full of tales of terrifying glimpses down apparently bottomless turquoise holes, and heart-stopping encounters with ice ladders.
The ever-widening crevasses are bridged by metal ladders, sometimes as many as five tied together end to end.
View from camp site: An awesome expanse of ice
Climbers have to pick their way across in their cumbersome crampons, clipped onto safety ropes, but knowing that one wrong step could put them in a lot of trouble.
Above the icefall is the Western Cwm, and Camp One - the first resting place for people heading for the summit.
Dirk described it as another world - a great white glacial valley.
Much has been made of the problem of pollution high on the mountain, but he and other climbers I've met say the efforts to clean up the area for this anniversary year have been effective.
Despite the numbers passing through Camp One, the mountainside still feels close to virginal.
For the 1953 team, the Khumbu Icefall gave great pause for thought.
Initially, it appeared impassable.
John Hunt, the group leader, recalled that "the ice resembles a gigantic cascade, pouring in leaping waves and eddies over submerged boulders towards us.
"Almost, you might expect to hear the roar of that immense volume of foaming water. But it has long been gripped by the intense cold, frozen into immobility."
After careful studying, they worked out a way through it - cutting their way up, past "monstrous ice boulders" and ice avalanches down the sides.
These days, expert climbing sherpas establish and maintain a route through the icefall every season. But those who've been through it say it's a heart stopping experience, even so.
For me, it's an adventure too far. We're already at 5,300 metres and that's as high as I want to go. From here on, my Everest experience will come through hearing other people's stories as I wait here in base camp.