The Great Wall of China was built over 2,000 years ago, by the first emperor of China during the Qin (Ch'in) Dynasty (221 B.C - 206 B.C.). In Chinese the wall is called "Wan-Li Changcheng" which means 10,000-Li Long Wall (10,000 Li = about 5,000 km).
After subjugating and uniting China from seven Warring States, the emperor connected and extended four old fortification walls along the north of China that originated about 700 B.C. (over 2500 years ago). Armies were stationed along the wall as a first line of defense against the invading nomadic Hsiung Nu tribes north of China (the Huns). Signal fires from the Wall provided early warning of an attack.
The Great Wall is one of the largest building construction projects ever completed. It stretches across the mountains of northern China, winding north and northwest of Beijing. It is constructed of masonry, rocks and packed-earth. It was over 5,000 km (=10,000 Li) long. Its thickness ranged from about 4.5 to 9 meters (15 to 30 feet) and was up to 7.5 meters (25 feet) tall.
During the Ming Dynasty (1368-1644), the Great Wall was enlarged to 6,400 kilometers (4,000 miles) and renovated over a 200 year period, with watch-towers and cannons added.
Badaling Great Wall
Badaling Great Wall is located at Yanqing County, more than 70 kilometers northwest from the center of Beijing City. It is a mountain pass of the Jundu Mountain. Badaling is at the highest point of north end of the Guan'gou gorge, in which the Juyongguan Pass lies. In the history, the function of Badaling was to protect the Juyongguan Pass. Along with Guan'gou gorge, there are several interests and historic sites. Badaling is a rare ancient military defense project. The elevation of it is about 1,000 meters.
The wall of Badaling has a total length of 3, 741 meters with an average height of 8 meters The highest part is 15 meters. The total area for a tour is 19, 000 square meters. The top of the wall can permit five horses to be ridden abreast. There are arched doors at the inner side of the wall with very little distance between each two doors. Thearched doors lead you to the top of the wall by stone stairs.
Beijing Mutianyu Great Wall
In the northern part of Huairou County some 70 kilometers north-east of Beijing City, Mutianyu Great Wall winds its way for over 2000 meters. The construction of Mutianyu Great Wall was started in the mid-6th century during China's Northern Dynasties (386 - 581) and what now remains is the main restoration made during the Ming Dynasty (1368 - 1644). It has served as a northern barrier of what is now Beijing through the ages. Connected with Juyongguan Pass in the west and Guibeikou Great Wall in the east, this section was built along steep ridges and deep valleys. Differing from that part of the Great Wall more widely visited, this section is renowned for its unique fortifications.
Beijing Simatai Great Wall
To the east of the Jinshanling stretch of the Great Wall there lies the quiet and remote Simatai Great Wall. The ruinous state of this part of the Wall gives it an air of authenticity that has earned it the reputation of being the most beautiful section of the 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.
Beijing Juyongguan Pass
Juyongguan Pass is located in an 18 kilometer-long valley named 'Guangou' which is inside Changping County more than 50 kilometers from Beijing City. It is one of the three greatest passes of Great Wall of China. This section is well preserved and is a good alternative for visitors who would like to avoid crowds along the highly popular Badaling section during holiday and peak seasons.