A Doukou on Mutianyu
A Doukou on Badaling
The Wall in Gansu
The Wall in Dunhuang
The constructions and facilities the wall are important parts of the overall defensive system of Chinese Great Wall.
Watch Tower:
A watch tower stands higher than the wall. There are two kinds of watch towers: solid watch towers and hollow watch towers. A solid watch tower has a solid base filled with earth and covered with bricks. The top of the tower is paved with bricks forming a platform. In the Ming Dynasty (1368 - 1644), people found the watch towers were more useful if the solid parts were built into houses for soldiers to live and hide in. Therefore, hollow watch towers gradually replaced solid towers. The hollow watch towers usually have two storeys: lower storey had rooms for soldiers to live in and to store food; while the upper storey was a platform for observing and shooting at enemies.
Juanmen
A Juanmen is an arch-shaped gate at the foot of the wall for the soldiers to ascend the wall. There are stone stairs connecting Juanmen and the top of the wall.
Duokou
Doukou is the toothlike wall facing the direction of enemies used to hide the soldier's body when observing the enemies. The little square hole on the upper part of Doukou was for observing the enemies, while the little square hole on the lower part of Doukou was for shooting arrows.
Yuqiang
Also named Nüqing, Yuqiang is a low wall paralleled to Doukou but lower than Doukou. It functions as a railing to protect the soldiers from falling down to the ground.
Packway
A packway is a slope connecting the ground and the top of the wall. It is 5 to 6 meters wide, which allows both horses and soldiers to pass, hence the name Ma Dao (mǎ dào, the path for horses). At the east and west sides of the gate tower in Jiayuguan Pass, there are wide packways.
Drainage Ditch
To remove water from the top of wall, drainage ditches were also built on Great Walls. The mouths of the ditch usually stretch out from the wall for one meter to keep the base of the wall from being eroded by water.
Qiangtai
Qiangtai is also called Mamian (the face of a horse) for it extrudes from the wall like a long horse face. It is a platform on the wall and has similar function with guard towers: soldiers can hide on Qiangtai and shoot enemies.
