Mauna Kea

The world's tallest mountain technically is not Mount Everest.

Mount Everest is the tallest mountain above sea level, but if we're talking sheer height here, base to summit, then the tallest mountain is Mauna Kea on the island of Hawaii.

Here's how it breaks down:

Everest stands 29,035 feet above sea level. Mauna Kea only stands 13,796 feet above seal level, but the mountain extends about 19,700 feet below the Pacific Ocean. Over half of it is submerged.

That puts the total height of Mauna Kea at about 33,500 feet - nearly a mile taller than Everest.