A NASA scientist uncovered a Cold War military base under ice in Greenland this April, as reported by NASA’s Earth Observatory on Monday. Several months ago, scientist Chad Greene was flying aboard a Gulfstream III with engineers in an effort to monitor a radar instrument on the Greenland Ice Sheet.

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.

NASA scientists have made a surprising discovery beneath Greenland's thick ice sheet: an abandoned Cold War-era military base called Camp Century, now buried 30 meters below the surface.