In Mauritania, hidden deep into the great Sahara desert, there is a huge and mysterious geologic formation that is hard to spot from ground level, walking around on Earth.

It turns out that we really discovered this incredible bull’s-eye in the sand only when we began sending humans into space when the Gemini IV mission (1965), a four-day orbit around Earth, the astronauts were asked to take photos of Earth’s terrain.

The Eye of the World, or Eye of Sahara more formally known as the Richat structure is a deeply eroded, slightly elliptical dome with a diameter of 40 kilometres and for a while, scientists did think that the Eye of the Sahara was an impact crater. But they didn’t find enough melted rock to make that guess hold water. Current theories suggest a much more complicated story behind this incredible natural formation.

The Eye’s formation began more than 600 million years ago, when molten rock pushed up toward the surface but didn’t make it all the way, creating a dome of rock layers. This also created fault lines circling and crossing the Eye. The molten rock also dissolved limestone near the center of the Eye, which collapsed to form a special type of rock called breccia.

A little after 100 million years ago, the Eye erupted violently. That collapsed the bubble partway, and erosion did the rest of the work to create the Eye of the Sahara that we know today. The rings are made of different types of rock that erode at different speeds. The paler circle near the center of the Eye is volcanic rock created during that explosion.

This fascinating structure is hard to reach on ground as it requires a lot of patience and resistence to the extremly hot temperatures of the Sahara desert, but the lucky few will be able to catch an unforgettable emotion.