NASA scientists have discovered a secret underground city thought to be the safest on earth, buried 100 feet beneath the ice of Greenland.

       Researchers were shocked last April when their advanced radar technology picked up signs of human construction deep beneath the ice of the island territory’s tundra, according to the space agency.

       Camp Century, as it was called, was a Cold War-era satellite for the U.S. Army used as a front for a planned arsenal of nuclear missiles.

       The camp was designed to be a city under the ice — with plans for over 3,000 miles of tunnels meant to provide a tactical advantage in a nuclear fight against the Soviet Union.

       The 21 tunnels that were built were cut into the ice sheet near the surface of the island.

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       The camp was built from 6,000 tons of material, transported via heavy bobsleds that topped out at two miles per hour.

       Camp Century operated from 1959 until 1967 but less than a decade after it was built the site was abandoned as ice began to crush the site and the area was sadly lost to the elements.

       There are still thousands of gallons of nuclear waste buried beneath the ice.

       Alex Gardner, a cryospheric scientist at NASA’s jet propulsion laboratory said: “We were looking for the bed of the ice and out pops Camp Century.

       "We didn’t know what it was at first. In the new data, individual structures in the secret city are visible in a way that they’ve never been before.”

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       In radar images of the site, Greene said, many of the base’s individual structures are clearly visible.

       To study the base, NASA used Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR), a technology that uses radio waves.

       The sprawling sub-zero tunnels are back in the limelight after the incoming US president reiterated his calls for the United States to be able to purchase Greenland.

       Donald Trump first expressed his interest in taking control of Greenland in 2019, when he raised the idea of buying the Denmark-owned island despite being told it was not for sale.

       Speaking at Mar-a-Lago on Tuesday, Trump insisted that the United States needed the island, as well as the Panama Canal, "for national security".