"I cannot believe what I saw up there." The harsh reality of climbing Mount Everest.

When the mind thinks of Mount Everest, the world’s tallest mountain, it likely conjures up images of jagged peaks covered in snow, with one or two brave adventurers who have climbed for months to conquer it.

Maybe it imagines the inhospitable conditions; strong, freezing winds or a deadly avalanche.

What it’s unlikely to think of is a traffic jam of brightly coloured backpacks and puffer jackets, as more than 100 climbers queue to reach the summit.

But that is what awaited those who reached Everest’s summit last week, as a photo by mountaineer Nirmal Purja captured on Wednesday.

Everest is the world’s largest open-air graveyard, littered with the bodies of those who have died while climbing it. Many bodies – most of which are in the death zone – have become markers for others attempting the climb.

Weather conditions, terrain and low oxygen levels make retrieving bodies on Everest near-impossible – and even if you’re willing to try, an expedition to recover remains from the death zone can cost more than AU$110,000.

If bodies are found, they are usually stuck to the mountain, frozen in place for good.

Green Boots.

Perhaps Everest’s most infamous marker is Green Boots, the frozen body of a fallen climber who earned his moniker because of his brightly coloured hiking boots.

Green Boots’ identity is widely believed to be Indian climber Tsewang Paljor, who lost his life in a 1996 blizzard after reaching the summit with two others.

The fourth member of their expedition, Harbhajan Singh, had urged the three men to abandon their attempt to summit due to incoming bad weather, but they persisted.

“Don’t be overconfident,” Singh insisted. “Listen to me. Please come down. The sun is going to set,” he told the men via walkie-talkie after abandoning his own attempt and descending back to camp.

Over time, Paljor became known as Green Boots and was a permanent fixture on the North Col passage, his body curled in a limestone alcove cave at 8500 m. His legs sprawled across the path, so everyone who passed needed to walk over them – a harsh reminder of the mountain’s brutality.

In 2014, climbers noticed that Green Boots had disappeared, but in 2017 several climbers believed he had once again become visible and was covered in stone.

Sleeping Beauty.

In 1998, Francys Arsentiev became the first woman from the United States to reach the summit of Mount Everest without the aid of bottled oxygen, but she and her husband Sergei never made it back down.

The pair reached the summit late in the day and were forced to spend another night above 8000m. During the night, Francys and Sergei became separated.

Sergei made his way down to camp, assuming that his wife had done the same. When he discovered her absence, he raced back up the mountain with oxygen and medicine, hoping to rescue her.

Accounts vary, but on May 23 an Uzbek team found Francys half-alive and unable to move without assistance. They carried her down as far as they could before their own oxygen ran out and they were forced to leave her and descend to camp. On their way down, they passed Sergei on his way up to her. He was never seen alive again and his body was not found until much later.

For nine years, climbers scaled around Francys, who became known as 'Sleeping Beauty', before her body was dropped to a lower location on the mountain face, out of view.

David Sharp.

In 2006, Green Boots' cave became even more infamous when British solo climber David Sharp was discovered huddled inside, barely alive.

He had successfully summited Everest on his third try and, during his descent, stopped to rest inside Green Boots' cave, just feet from Green Boots himself.

Sharp drew his legs to his chest and rested his head upon his knees. At the time, media widely reported that Sharp moaned and murmured as around 40 climbers passed him without offering any aid. He died later that day, alongside Green Boots.

Sharp's death caused major controversy within the climbing community, with Sir Edmund Hillary - the first person to ever successfully summit Mount Everest - detesting the attitudes of climbers as "horrifying".

"A human life is far more important than just getting to the top of a mountain," he told the New Zealand Herald.

A year later, Sharp's body was removed from sight at the request of his parents.

Melting ice means... more bodies.

More than 300 people have died on Mount Everest, and the vast majority still remain there.

While the remains are perfectly preserved in the mountain's freezing temperatures, warming temperatures attributed to climate change are exposing bodies that had been covered in ice and snow for decades.

"Because of global warming, the ice sheet and glaciers are fast melting and the dead bodies that remained buried all these years are now becoming exposed," Ang Tshering Sherpa, former president of Nepal Mountaineering Association, told BBC News in March.

"We have noticed that the ice level at and around the base camp has been going down, and that is why the bodies are becoming exposed."