As a NASA science flight was flying over the Greenland ice sheet this spring, a surprise popped up on a specialty radar: a hidden Cold War city more than 100 feet beneath the ice.

Scientists now have a clearer picture of Camp Century, an abandoned U.S. military base long hidden under the ice in Greenland, thanks to a NASA research team's good luck.

As it turns out, this abandoned "secret city" was the site of a secret Cold War project known as Project Iceworm which called for the construction of 2,500 miles (4,023 km) of tunnels that could be used to nuclear intermediate range ballistic missiles (IRBMs) at the Soviet Union.