Strictly speaking, The Great Wall of China isn’t a single wall. It’s a complex network of walls, barracks, watch-towers, and other fortifications, and construction on early versions of it might’ve begun more than 2500 years ago. Each of these successive works was, for its time, an astonishing feat of engineering—even if none of them were ever, as the myth goes, visible from space. All of them shared a common purpose, which was to help defend the northern states of China against invasions from various peoples of the Eurasian steppes in and around what is today Mongolia.
This is not quite the story told by Zhang Yimou’s 2016 film The Great Wall, starring Matt Damon, Jing Tian, Pedro Pascal, and Andy Lau—most especially because the real Great Wall has nothing to do with a meteor and rage-fueled lizard dogs from space.