Construction of the Great Wall started in the 7th century B.C. The vassal states under the Chou Dynasty in the northern parts of the country each built their own walls for defense purposes. After the state of Chin unified China in 221 B.C., it joined the walls to hold off the invaders from the Tsongnoo tribes in the north and extended them to more than 10,000 li or 5,000 kilometers. This is the origin of the name of the 10,000-li Great Wall.
The Great Wall was renovated from time to time after the Chin Dynasty. A major renovation started with the founding of the Ming Dynasty in 1368, and took 200 years to complete. The wall we see today is almost exactly the result of this effort. With a total length of over 6,000 kilometers, it extends to the Jiayu Pass in Gansu Province in the west and to the mouth of the Yalu River in Liaoning Province in the east.
The Great Wall, (Wanli Changcheng) literally means the Ten Thousand Mile Wall, is a great fortification in ancient China. Badaling,Mutianyu and Simatai are the three most famous sections of the great wall.

Badaling great wall

The section at Badaling is the most famous of all due to its proximity to Beijing City and condition of restoration. The imposing Badaling Great Wall climbs up and down, twists and turns along the high mountain ridges. It fully shows the lofty quality of ancient Chinese labor people.
Badaling Great Wall, with more than 1000 meters above sea level, occupies a commanding and strategic position. It is a defensive outpost of the Great Wall. It is called "Bada" as it stretches in all directions.
Badaling Great wall was built in the 18th year of the Ming Hong Zhi reign (1505). The wall, built with high stone slabs on the outside, is 7.8 meters high on the 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 wall is wide enough for five horses to gallop abreast and ten people to advance shoulder to shoulder. The outside of the wall is called rampart wall. The rampart wall was built with bricks 1.7 meters high. 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 is a stone ladder for climbing up and down.

Mutianyu great wall

Located in Huairou County 70km northeast of Beijing, Mutianyu section of Great Wall is connected with Juyongguan Pass in the west and Gubeikou Gateway in the east. As one of the best-preserved parts of the Great Wall, Mutianyu section of Great Wall used to serve as the northern barrier defending the capital and the imperial tombs. First built in the mid-6th during the Northern Qi dynasty, Mutianyu Great Wall is older than Badaling Great Wall. In the Ming dynasty, under the supervision of General Xu Da, construction of the present wall began on the foundation of the wall of Northern Qi. In 1404, a pass was built in the wall. In 1569, the Mutianyu Great Wall was rebuilt and till today most parts of it are well preserved. The Mutianyu Great Wall has the largest construction scale and best quality among all sections of Great Wall.

Built mainly with granite, the wall is 7-8 meters high and the top is 4-5 meters wide. Comparing with other sections of Great Wall, Mutianyu Great Wall possesses unique characteristics in its construction.

Simatai great wall

Unlike the sections to be seen at Badaling or Mutianyu that have undergone extensive restoration, the wall at Simatai has received very little attention. Here, the wall really looks as one would expect it to look some 500 years after it was built during the Ming Dynasty. The local people are proud of this monument and proclaim that it was as a consequence of visiting Simatai that UNESCO was convinced the wall should be listed as a World Heritage site. It towers over the nearby villages and farmland as it winds its way like the spiny back of a dragon over the sharply clipped peaks of the mountains.

Because this section has retained much of its original 500 year old features it offers a quite hazardous passage to those who wish to walk along it. Needless to say, the inherent dangers offer a challenge that is quite inresistable to dedicated hikers in quest of adventure. An additional attraction is that as Simatai is some 130 kilometers (80 miles) to the north-east of Beijing it is well beyond the reach of the huge crowds of tourists that throng the more popular and accessible parts of the Wall.

Huangyaguan Great Wall

28 km north of Jixian Country, which is about 120 km north from Tianjin, there is another section of the Great Wall which is less known to foreigners. The Great Wall at Huangyaguan was originally built in 557 and rebuilt during the Ming Dynasty. This section of the Great Wall has features different with those in Beijing. There is now an international marathon held on the Great Wall annually.

140 kilometers at the north-east end of Beijing City, there is a section of the Great Wall, called Jinshanling Great Wall. It is 90 kilometers to the Mountain Resort of Chengde. A tablet with the Chinese inscription of "Jinshanling Great Wall" was set in this section.

Jinshanling Great Wall

On the right is the full view of the Jinshanling Great Wall. Its east end connects to the Simatai Great Wall. Jinshangling Great Wall got its name because it was built on the bigger and the smaller Jinshan Mountains.

The Jinshanling Great Wall was initially built from 1368 to 1389 in the Ming Dynasty, and in 1567 or 1570 rebuilding of the Wall was mainly directed by General Qi Jiguang. Poems and tablet writings can be found on the Jinshanling Great Wall left from the time Qi Jiguang directed building of this section of the Great Wall.

The total length of this section is about eleven kilometers (6.8 miles), and the scenic spot of the Jinshanling Great Wall has an area of 32 square kilometers. The Wall is about seven to eight meters high and five to six meters wide, which is made of brick and stone. The Jinshanling Great Wall has an elevation of 700 meters. Watching Beijing Tower is on the highest position, from which you can see Beijing. The Jinshanling Great Wall is second only to the Badaling Great Wall in its completeness.