You don't see any ruins. You see a slight bumps in terrain or grass patches that turn yellow a few days earlier each year. Only taking a picture from hundreds of feet above, with favorable lighting when shadows are long reveals regular rectangles, old plough marks and shapes of buildings that were leveled thousands years ago earlier. People like Podebard would come back to the same places for years just to catch that ideal conditions and discover additional detail or missed structures that were not visible on any previous picture.