Archaeologists have uncovered hundreds of mysterious stone formations hidden in one of the most extreme environments on Earth: Harrat Khaybar, a vast lava field in northwestern Saudi Arabia. Nicknamed the “gates of hell” for its volcanic scars and desolate terrain, the site is now revealing signs of prehistoric human presence dating back up to 9,000 years. These include rudimentary villages, intricate stone fences, and the more puzzling forms known as “desert kites” and “gates.”Unraveling The Desert Kites“Desert kites” are long, funnel-shaped stone structures that stretch across the terrain, visible only from above. Credit: CNES/Airbus, via Google EarthThe Gates That Lead To QuestionsThe so-called “gates” are even more confounding. Built on volcanic domes—some of which were once active—the gates consist of roughly assembled, low stone walls.