The Great Wall has a long history and is a magnificent project. It is one of the new seven wonders, ranking first in the selection of "New Seven Wonders of the World". (Because of online voting, China has a large population and the Great Wall has taken advantage of it. You are not a hero until you reach the Great Wall. The Great Wall criss-crosses the east, west, north and south, stretching and undulating on the vast land of our great motherland. It is like a dragon, crossing towering mountains, vast grasslands, vast deserts and heading for the vast sea. According to historical documents, more than 20 vassal states and feudal dynasties built the Great Wall. If you add up the Great Wall built in past dynasties, it is about 10 Wan Li. The length of the Great Wall in Qin, Han and Ming Dynasties exceeded 1 Wan Li. At present, Xinjiang, Gansu, Ningxia, Shaanxi, Inner Mongolia, Shanxi, Hebei, Beijing, Tianjin, Liaoning, Jilin, Heilongjiang, Henan, Shandong, Hubei, Hunan and other provinces, cities and autonomous regions have the remains of the ancient Great Wall and beacon towers. Among them, the Great Wall of Inner Mongolia Autonomous Region alone reaches 3 Vandory.
In the Ming Dynasty, in addition to the "outer" Great Wall, the "inner" Great Wall and the "inner three passes" Great Wall were also built. The "Neiguan" Great Wall, based on the Northern Qi Dynasty, starts from Pianguan at the junction of Inner Mongolia and Shanxi in the west, Yanmenguan and Pingxingguan in the east, enters Hebei, then turns to the northeast, passes through Yuanyuan, Fangshan and Changping counties, reaches Juyongguan directly, and then reaches Huairou Siguan from north to east, and is connected with the "Outer" Great Wall, with Zijingguan as the center, showing a general north-south trend. The "Neisanguan" Great Wall is parallel to the "Inner" Great Wall in many places. In some places, the two cities are only tens of miles apart. In addition, a large number of "heavy cities" have been built. There are 24 "heavy cities" in Yanmenguan area!
The Great Wall is a miracle created by working people in ancient China. Since Qin Shihuang, building the Great Wall has been a big project. According to records, Qin Shihuang used nearly one million laborers to build the Great Wall, accounting for 1/20 of the national population! At that time, there was no machinery, except for animals that could climb mountains, such as donkeys and goats. The working environment was steep mountains and steep cliffs. It is conceivable that this huge project could not be completed without a large number of people working hard.
According to a rough estimate, the number of the Great Wall in Wan Li only existed in the Ming Dynasty. If a wall with a thickness of 1 m and a height of 5 meters is made of masonry and earthwork, it can surround the earth for more than one week. If it is used to pave a road with a width of 5 meters and a thickness of 35 centimeters, it can circle the earth three or four times. If you count the total 10 Wan Li built in past dynasties, this long wall can go around the earth for more than ten times, and this road can go around the earth for thirty or forty times.
Building the Great Wall is an important experience, which was affirmed by Qin Shihuang, Sima Qian wrote in Historical Records. After that, every dynasty built the Great Wall according to this principle. All the passes in Guancheng are built between two high mountains and canyons or at the bend of the river. Or places that will pass by, in order to control the danger, save manpower and material resources, and achieve the effect of "one person guards it, and ten thousand people can't force it". Building castles or beacon towers is also an option in Four Essentials. As for building city walls, it is more important to make full use of the terrain. For example, Juyongguan and Badaling Great Wall are built along the back of the mountain. Some sections are very steep from the outside of the wall, but they are very gentle inside, which has the effect of "easy to defend but difficult to attack". In Liaoning Province, the Great Wall of Liaodong Town in Ming Dynasty was called the Mountain Dangerous Wall and the Split Gable, which was made by slightly splitting the steep cliff. Some places completely use cliffs, rivers and lakes as natural barriers, which can be said to be wonderful. As a great project, the Great Wall has become a precious heritage of the Chinese nation.