Mount Everest represents the highest spot on earth, but it is not the tallest mountain in the world. Mount McKinley in Alaska is the tallest mountain based on measurements taken from the base of the mountain, which is above sea level, to the peak. However, Mauna Kea in Hawaii is the actual tallest mountain in the world measured from its base, of which most of it is under water. Collectively, it rises 6.3 miles (10,200 m) from the base beneath the sea to the peak at 13,796 feet (4,205 m).