Almost all of the world's finest ground-based observatories are located on mountains -- for a variety of reasons.

First and foremost, starlight appears less distorted in the thin atmosphere on mountaintops. Mountaintops also have unobstructed views of the horizon in all directions. Lastly, most cities and towns -- with their accompanying light pollution -- are situated in valleys and plains, so remote mountaintops are among the last places on Earth to find the dark skies so sought after by astronomers.