Aconcagua, 6,960.8 m (22,837.3 ft).
In mountaineering terms, Aconcagua is technically an easy mountain if approached from the north, via the normal route. Aconcagua is arguably the highest non-technical mountain in the world. But the effects of altitude are severe (atmospheric pressure is 40% of sea-level at the summit) so multiple casualties occur every year on this mountain (in January 2009 alone five climbers died). So this is a serious mountain with serious risks. Many climbers underestimate the objective risks of the elevation and of cold weather, which is the real challenge on this mountain.
Johan Ernst Nilson has done two expeditions to Aconcagua where they had to turn around the first time and the second time reaching the summit. The Polish Glacier Traverse route, crosses through the Vacas valley, ascends to the base of the Polish Glacier, then traverses across to the normal route for the final ascent to the summit. This is a fantastic route with beautiful nature and scenic views over the mountains. Only 43% attempt The Polish Glacier Route.

Together with his climbing partner Nicolas Gafgo, Johan summited in 2006. On the way down Johan suffered from AMS, Altitude Mountain Sickness and was in really bad shape when entering Basecamp. He had to spend the night in the medical tent with oxygen and medical treatment.