Please tell me one of the wonders of China.

The Great Wall has a long history and a magnificent project. It is one of the new seven wonders and ranked first in the "New Seven Wonders of the World" selection activity. (Because of the online voting, China's large population also makes the Great Wall take advantage of it.) He who doesn't reach the Great Wall is not a hero. The Great Wall crisscrosses the east, west, north and south, rolling on the vast land of our great motherland. It's like a dragon, crossing the lofty mountains, the vast grassland, the vast desert and heading for the vast sea. According to historical documents, more than 2 vassal states and feudal dynasties built the Great Wall. If the Great Wall built in different times is added up, there are about 1 Wan Li. Among them, the length of the Great Wall built by the Qin, Han and Ming dynasties exceeded 1, 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 addition to the "outer" Great Wall, the Ming Dynasty also built the "inner" Great Wall and the "inner three passes" Great Wall. The "Neiguan" Great Wall, based on the Northern Qi Dynasty, starts from the west of Pianguan at the junction of Inner Mongolia and Shanxi, passes through 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 goes from north to east, reaches the Four Customs in Huairou, and connects with the "Outer" Great Wall, with Zijingguan as the center, and generally runs in a north-south direction. The "Inner Three Pass" Great Wall runs parallel to the "Inner Side" 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. Building the Great Wall has been a big project since Qin Shihuang. According to records, Qin Shihuang used nearly one million laborers to build the Great Wall, accounting for 1/2 of the national population! At that time, there was no machinery, except for animals that could climb mountains with donkeys and goats, and 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 engineering quantity of the Great Wall in Wan Li is only built in the Ming Dynasty. If the masonry and earthwork are used to build a wall with a thickness of 1 meter and a height of 5 meters, 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 go around the earth three or four times. If the total amount of 1 Wan Li built by all dynasties is calculated, this long wall can go around the earth for more than ten weeks, and this road can go around the earth for thirty or forty weeks.

"Because of the terrain, blocking traffic with danger" is an important experience in the construction of the Great Wall, which was affirmed by Qin Shihuang and written by Sima Qian in Historical Records. Every dynasty built the Great Wall in the future according to this principle. All the passes in Guancheng are built between two mountain canyons or at the turning point of the river. Or a place that would pass by, so as to control the danger and save manpower and materials, so as to achieve the effect of "and while one man guards it, ten thousand cannot force it". Building castles or beacon towers is also a choice in "four important places". As for building city walls, it is more important to make full use of the terrain. For example, the Great Wall in Juyongguan and Badaling is built along the back of mountains, and some sections are very steep from the outside of the city walls, while the inside is very gentle, which has the effect of "easy to defend but difficult to attack". In Liaoning province, the Great Wall in Liaodong Town in Ming Dynasty was called Mountain Dangerous Wall and Split Mountain Wall, which was built by using steep cliffs and chopping the cliffs slightly. In some places, cliffs, rivers and lakes are completely used 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.