Since Edmund Hillary and Tenzing Norgay first reached the summit of Mount Everest in 1953, conquering the world's highest peak has been a goal of almost every serious mountaineer on the planet. But this famous peak pales in comparison to two secret mountains, which are more than 100 times taller than Everest's 8,800-meter summit, scientists have discovered, The Daily Mail reports.

Reaching heights of around 620 miles (1,000km) these continent-sized “islands” of rock dwarf anything else found on our planet.

But scientists from Utrecht University have revealed that these gargantuan peaks are not found on our planet's surface.

Instead they are buried some 1,200 miles (2,000km) beneath our feet.

The researchers estimate that the mountains are at least half a billion years old but could date back to the formation of Earth four billion years ago

Lead researcher Dr. Arwen Deuss says: “Nobody knows what they are, and whether they are only a temporary phenomenon, or if they have been sitting there for millions or perhaps even billions of years.”

The two monstrous structures sit on the boundary between Earth's core and the mantle, the semi-solid area beneath the crust, beneath Africa and the Pacific Ocean.

Around them is a 'graveyard' of sunken tectonic plates which have been pushed down from the surface in a process called subduction.

In a new study, researchers found that the islands are much hotter than the surrounding slabs of the Earth's crust and many millions of years older.