The mysterious structure is over 1 billion years old.

Credit: Universal History Archive/UIG via Getty Images

Kondyor Massif had long puzzled scientists. Geologists pondered over whether the geological phenomenon located in eastern Siberia, Russia was a crater caused by a volcanic eruption, or something entirely different.

It turns out the mysterious spot, nicknamed "Treasure Island," is what's called an "intrusion."

Described by NASA as a “perfect circular intrusion,” Kondyor Massif is approximately six miles in diameter and 2,000-feet-high. The igneous creation formed more than 1 billion years ago after molten magma crystallized under the earth’s surface, forming the ring, the Siberian Times reported. Erosion eventually made the circle of rock visible.

Kondyor Massif earned its "Treasure Island" nickname as it contains some of the most precious metals in the world, including gold, platinum, and its own unique mineral, Konderite, which combines copper, platinum, rhodium, lead, and sulfur. Miners removed four tons of platinum here annually.

The river that flows out of the intrusion, fueled by melting snow waters, contains rare placer deposits of platinum crystals that can be found along the banks, according to NASA.

Sometimes mineral dealers even discover gold-encrusted crystals that are sold as jewelry, Atlas Obscura reported.

As Kondyor Massif is still an active mine, travelers interested in visiting it need a special permit. Those who get their permit then need to fly to Mar-Kuel and drive five hours or take a helicopter to see the intrusion in person, according to the website To Discover Russia.