Mount Neverrest is the highest peak of the world in the DuckTales universe. It is presumably somewhere in the Himalayas. No person has ever reached the summit of Mount Neverrest, with George Mallardy and Scrooge McDuck getting the closest to it.
Mount Neverrest is impossible to climb not only because of the freezing cold, the regular snowstorms and the deep ravines, but also because of the random wormholes. Thus, wherever you climb, you cannot predict where you'll end up next, and it is impossible to find your way down.
It is based on Mount Everest, the highest peak in real life.