Its common knowledge that Mt Everest is a dangerously gruelling mountain climb, that it requires the absolute peak of physical endurance and conditioning, and that many have died during the attempt. Today I came across an article that explains how above 26,000 feet (the so called "Death Zone") the air is so thin that the recovery of bodies is impossible.

Every year about a thousand people on average attempt the summit, and on average about 20 of them die during the attempt.

The bodies of 216 unfortunate climbers still lay exactly where they fell, remarkably preserved even after decades in some cases.

WARNING: Interesting article, but somewhat gruesome (dead bodies). Possibly NSFW?
http://sometimes-interesting.com/2011/06/29/over-200-dead-bodies-on-mount-everest/