If mountains were measured from their base rather from sea level, this would be the world's tallest, since its base is on the ocean floor. Which mountain is this?

While Mount Everest is famously the highest mountain in terms of altitude above sea level, the title of the world's tallest mountain from base to peak belongs to a dormant volcano in Hawaii. The key to this distinction lies in where the measurement begins. More than half of Mauna Kea's immense structure is hidden beneath the Pacific Ocean, resting on the deep ocean floor.

From its underwater base, Mauna Kea rises for nearly 6,000 meters before it even breaks the surface of the water. Its peak then continues upward for another 4,208 meters (13,796 feet). When measured in its entirety, its total height is over 10,000 meters, making it significantly taller than Mount Everest's elevation above sea level. Everest's impressive height is measured from a starting point already high up on the Tibetan Plateau.

This incredible height and its isolated location make Mauna Kea's summit an ideal place for astronomical observation. The peak sits above most of the atmosphere's water vapor, providing exceptionally clear and stable air. This allows the powerful telescopes housed in the many observatories on its summit to capture stunningly sharp images of the cosmos from the top of what is, by one measure, our planet's tallest peak.