This is part of BBC Future’s “Best of 2015” list, our greatest hits of the year.

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“It is clear that the stake [the mountaineer] risks to lose is a great one with him: it is a matter of life and death…. To win the game he has first to reach the mountain’s summit – but, further, he has to descend in safety. The more difficult the way and the more numerous the dangers, the greater is his victory.”

- George Mallory, 1924

As though napping, the climber lies on his side under the protective shadow of an overhanging rock. He has pulled his red fleece up around his face, hiding it from view, and wrapped his arms firmly around his torso to ward off the biting wind and cold. His legs stretch into the path, forcing passers-by to gingerly step over his neon green climbing boots.

His name is Tsewang Paljor, but most who encounter him know him only as Green Boots. For nearly 20 years, his body, located not far from Mount Everest’s summit, has served as a grim trail marker for those seeking to conquer the world’s highest mountain from its north face. Many have lost their lives on Everest, and like Paljor, the vast majority of them remain on the mountain. But Paljor’s body, thanks to its prominence, came to be one of the most well-known.