While flying roughly 150 miles east of northern Greenland’s Pituffik Space Base, the NASA researchers also snapped photos of the polar landscape from the plane’s windows showing a barren, icy expanse. It wasn’t until analyzing the radar images, however, that the team realized what they had flown over without even realizing it.

Camp Century, a subterranean military base in Greenland, was spotted under the icy expanse during a flight earlier this year.

Project Iceworm sought to use Northern Greenland as a launch site due to its proximity to the Soviet Union and because of the remoteness of the location, according to the 2007 art

"We were looking for the bed of the ice and out pops Camp Century," NASA cryospheric scientist Alex Gardner said.