What is the main part of the ancient city of China?

In ancient times, city refers to city walls and moats, and can also refer to cities in general. This city, also known as battlements, is an ancient military defense building in East Asian countries such as China and South Korea. City, also called city wall, refers to the city wall, which is an ancient military defense building in East Asian countries such as China and South Korea. In order to protect people's lives and property, building cities is a tradition in East Asian countries. Compared with European countries, the battlements in East Asia are generally larger. According to different levels, cities can be divided into government level, county level, departmental level, fort level and so on. Generally speaking, the higher the level, the larger the scale, and the different official buildings. Most of the early cities in the ancient city of China were made of mud. After the Ming Dynasty, walls in various places began to be bricked on a large scale. Therefore, in most of China's ancient history, the cities were all yellow and bald. As early as 3000 years ago in Shang Dynasty, the ancestors of China had mastered the plate-making technology. The so-called plate building means that when building a wall, two plates (plates) are sandwiched in the middle, the width between the two plates is equal to the thickness of the wall, the plates are supported by wooden columns, then the soil is filled between the two plates, the wooden columns are built (rammed) tightly with pestle, and then the plates and columns are removed to form a wall. During the Spring and Autumn Period and the Warring States Period, the board-making technology was greatly improved, and the hanging board tamping method was widely used, that is, the wooden sticks passed through the plywood on both sides, fixed with ropes and straightened, and filled in the middle. This is the method mentioned in the Book of Songs. The wall built by this method is stronger than before, so it can eliminate the slopes on both sides in the old method and increase the difficulty of climbing the wall. At that time, some city walls were built of adobe (the size of a single adobe was about 1m×0.4m×0.2m), and they were staggered up and down to improve the density and strength of the city walls. Since the Spring and Autumn Period, cities in China have always adopted this simple method of clay construction. Nearly two thousand years later, the wall of the famous Yuan Dynasty Capital (Beijing) was still made of rammed earth. This kind of earthen city wall is not very beautiful, nor is it very strong, especially when it rains, it will be eroded and damaged by rain. Of course there are exceptions. For example, the Tongwancheng built by Helian Bobo, a Xia country in the Sixteen Countries of the Eastern Jin Dynasty (reigned from 407 to 425 AD), is a miracle in the history of tucheng construction. Copper Bowl City adopts the method of "steaming soil to build a city", that is, it is made by mixing glutinous rice juice, clay, sand and hydrated lime. Although it is a earthen city, it has the same hard texture and anti-destruction ability as stone. Legend has it that General Chigan Ali, who was in charge of the construction, was very strict and almost cruel. He ordered people to test the wall with an iron cone. Anyone who gets an inch in the cone will immediately kill the craftsman and fill the body into the wall. Under this crazy high-pressure policy, Tongwan City, which took six years to build, has excellent building quality. "Strong enough to sharpen knives and axes", which can be compared with modern cement. Of course, this is only a special case. In order to ensure the firmness and strength, most earth walls can only be close to the height, size and thickness. For example, more than two thousand years ago, the wall of Linzi, the capital of Qi State, was 20 meters wide, and the wall of Ying, the capital of Chu State, was 14 meters thick. In the era of cold weapons, such thickness and such combat capability are reassuring. In addition, to be on the safe side, in addition to the tall and thick city walls, parallel to the city walls, there are also wide and deep trenches dug manually (which can also be used to divert the river and become a moat). A metropolis, the moat around the city, is generally 30 meters wide and 4~5 meters deep. However, Tucheng also has the advantages of Tucheng, which is easy to repair. For example, when Li Guangbi was guarding Taiyuan in the Anshi Rebellion, Shi Siming's army was approaching, and it was definitely too late to reinforce Taiyuan, 40 miles away from Fiona Fang. So he led the soldiers and civilians to dig trenches outside the city, ordered people to make the dug trenches into hundreds of thousands of adobe bricks, and ordered people to build camps with adobe. They patched up the damaged places with adobe. From the perspective of military defense, the construction of ancient cities in China can be described as exquisite layout and heavy organs. At the top of the tall city wall, there is a continuous concave-convex tooth-shaped low wall built on the outside, which is called crib mouth, also known as crib wall. There is a crib for archery and observation above, and a ventilation hole to protect the wall below. The inner low wall is called the female wall, also called "arrogance". Generally lower than a crib, it acts as a guardrail to prevent soldiers from falling when walking back and forth. In addition, there are Ring Road and Dengcheng Road within the city wall. There are towers in the center of each gate of the city wall, which are exquisite and beautiful high-rise buildings on the top of the city wall. It is an important high-altitude defense facility in the ideal city to climb the mountain on weekdays and wait and see, and the main meeting will take command in wartime. On the outside of the tall city wall, there will be a section protruding from the outside of the city wall at regular intervals. This is the horse face (also known as the enemy platform, pier platform and wall platform). There are two kinds of horse faces, rectangular and semi-circular, which are named after their long and narrow shapes. The purpose of the horse face is to interact with the city wall, eliminate the dead angle at the gate, and attack the enemy from top to bottom on three sides. Its general width is 12 ~ 20m, protruding from the outer surface of the wall by 8 ~ 12m, and the spacing is 20 ~ 250m (generally 70m). This is exactly in line with the record in the eight-part essay "Guarding the City" in the Song Dynasty: "Horse face, the old system is 60 steps and one step, jumping out of the city, not reducing two feet, the width is uncertain with the geographical location, and the two sides look straight at the corner of the city, and there are buildings on it." In the era of using cold weapons, this distance is just within the effective range of throwing stones with bows and arrows. In order to enhance the defensive and war capabilities of the horse face, enemy towers are generally built above the horse face, which can be used for garrison and observation, and can also store weapons, so that the defensive performance of the city wall can be fully exerted. In wartime, we can use its prominent tall buildings to wait for opportunities, observe the enemy's situation and prevent the enemy from attacking the city around the city; It is also an important part of the city wall defense project to rely on the cross fire of the enemy tower from the front and between the left and right buildings to connect points and lines at any time and weave a tight high-altitude fire net to attack the enemy. In addition, there is a tower at each corner of the city wall, which is called the turret. The turret is oriented at an angle of 135 degrees with the big wall, and its height and volume are between the turret and the enemy tower. It is mainly used to make up for the weak defensive links at the corner of the city wall, thus enhancing the defensive ability of the whole city wall. In wartime, the defenders in the turret are commanding and have a wide field of vision, so they can monitor and attack the invading enemy from all angles. From the point of view of military attack, the weakest link in an ideal city is naturally the gate. Therefore, urban designers will naturally increase protection and strengthen defense capabilities. Smaller cities are usually equipped with hanging doors or bridges, while larger cities are equipped with clay pots. Wengcheng is a small town built outside the city gate, also known as Moon City, which is specially used to defend the city gate. The previous episode of the martial arts master guarding the city recorded: "Is the urn outside the city round or square? Depending on the terrain, it is as high and thick as a city, but it is open to the left and right. " Even if the enemy breaks through the urn door, there is still a front door defense. Because the place in the urn is relatively narrow, it is not easy to launch a large-scale attack, which slows down the enemy's attack speed, while the defenders at the top of the city wall can shoot from all directions, giving the enemy a fatal blow. "The Book of Songs Zheng Feng Out of the East Gate" says: "There is a young woman." "Dark and bright" refers to Wengcheng. It can be seen that as early as the Spring and Autumn Period, urban defense technology has reached a fairly perfect level. The three-dimensional urban defense pattern consisting of city walls, towers, moats, horse faces, watchtowers, turrets and crocks basically matured in the Spring and Autumn Period and the Warring States Period, and continued until the Ming and Qing Dynasties.