As early as the Warring State period (475-221BC), three northern kingdoms in China built Great Walls in their own territory as the military defense project.
After unifying all seven kingdoms, Qinshihuangdi, the first emperor of Qin Dynasty (221-206BC) conscripted more than one million people, which means 20% of total population to build massive Great Wall as well as link up individual Great Walls to protect the newly established regime. As the result, Qin Great Wall expanded over 6,700 km in northern China. Many important passes and famous sections appeared as well.
Located more than 70 kilometers northwest of Beijing City, Badaling Great Wall is one of the most famous sections. With general elevation of 800 meters above sea level, this section of the wall occupies a commanding and strategic position and serves as the outpost of the Great Wall.
Badaling Great wall was re-built in 1505 of Ming Dynasty (1368-1644). The wall, built with high stone slabs on the outside, is 7.8 meters high on average, some even reaches 8.4meters. The base of the wall was built with more than 2000 large rectangular slab of granite stones. It is about 6.5 meters wide on the average at its base and 5.7 meters wide on the average on the ramparts. The outside of the wall is called rampart wall which was built with bricks over 1.7 meters high. The wall is wide enough for five horses to gallop abreast and ten people to advance shoulder to shoulder.
Built for the purpose of defense, there are holes on the tip of the wall called watch-hole, and peepholes under the wall called embrasures. Inside of the wall, there are low walls with one meter high called parapets, which can be used as railings. There is a scroll door not far from the inside wall, with a stone ladder for climbing up and down. The wall is narrow on the top and broad on the bottom forming an adder-shape structure. This made the wall stands firmly on the rise and fall ridges. The wall was built with 10-14 rectangular slab of stones surrounding its outside, filled with soil sand stones in the middle, and paved with square bricks on the top between the bricks were stuck with lime stones. This makes the wall tidy, beautiful, and firm. There are gutters with gargoyles to drain rain-water off the parapet wall.