The Great Wall of China was not built as a single, continuous wall but as a series of projects undertaken by different dynasties over many centuries. These projects varied in purpose, materials, and design. The popular tourist spots like Badaling and Mutianyu are highly restored parts of a structure that started during the Warring States period and reached its most recognizable form during the Ming dynasty. Construction of the wall began as early as the 3rd century BCE and continued until the Ming dynasty (1368–1644). The best-preserved sections, often seen in postcards and travel photos, are primarily from the Ming era. The First Emperor of China, Qin Shi Huang, connected existing walls in the north to protect against invasions. Later, the Han dynasty extended the wall further west to safeguard the Silk Road trade routes. The Ming dynasty completely reimagined the wall, adding regular watch towers and using more advanced construction methods. One notable technique involved mixing sticky rice into the mortar, which helped strengthen the structure. The Great Wall is gradually disappearing due to slow erosion rather than a sudden disaster. In Gansu province, researchers are using drones and 3D modeling to study salt erosion, a process where salty water seeps into the wall’s foundation, weakening it and causing parts to collapse. Human factors have also contributed to its degradation, including villagers taking bricks for building homes and damage from wars. During the Cultural Revolution, Mao Zedong encouraged peasants to remove bricks from the wall, a practice that had roots in local traditions. Efforts to preserve the Great Wall began in 1987 with the founding of the China Great Wall Society, which has worked alongside a 2006 law aimed at protecting the structure. The society reports that human-caused damage, especially from construction projects approved by local governments, is a growing concern. Drones equipped with low-altitude oblique photography technology are now used to create detailed digital maps of the wall, helping experts assess and monitor damage more effectively. A widely believed myth is that the Great Wall of China can be seen from space. However, it is not visible from Earth orbit or even from the Moon. The wall’s composite and widespread nature makes it difficult to define exact contours, and its visibility from space remains a misconception.