The Great Wall

     The Great Wall is a symbol of China, and a witness to the long history of the country and a crystallization of the wisdom, strength and will of the ancient Chinese. In 1987 the Great Wall was inscribed on the World Heritage List by the United Nations Educational, Scientific and Cultural Organization.

    In the Warring States Period, various states built their own walls to guard against invaders, and the walls were located in the valleys of the Yellow and Yangtze rivers. After unifying China, Emperor Shihuang of the Qin Dynasty dismantled most of the walls, and shifted the defense to the north against the Huns. The emperor sent general Meng Tian on a northern expedition, and began construction of the Great Wall. Making use of geographic conditions, the general built watchtowers and fortifications along the Yellow River and the Yinshan Mountains, and connected the extant walls of the former Yan and Zhao states in the north and the east and those built by King Zhaowang of the smaller Qin state in the west. The completed Great Wall extended from the Liaodong Peninsula in the east to Lintao of Gansu Province in the west, measuring more than 10,000 li (one li is about 0.5 km) in length. In the Han Dynasty, Emperor Wudi, who ruled from 133 BC to 87 BC, ordered generals Wei Qing and Huo Qubing to attack the Huns,  and repair the Great Wall and add new sections to it. The Great Wall of the Han Dynasty extended more than 2,000 li westward, to the west of Jiuquan and Dunhuang in Gansu Province.

    To protect the country against Tartars from the north and Nuchens from the northeast, the Ming rulers kept building the Great Wall ever since the dynasty was founded. For more than 200 years, the Ming empire implemented 18 large-scale construction projects and built a Great Wall of 6,700 km, extending from Jieshi in the east to Jiayu Pass in the west.

    As a comprehensive defense system, the Great Wall consists of passes, walls, watchtowers, and beacon towers. The walls are the major part of the Great Wall, and they are usually built along mountains. The western parts of the Great Wall are mostly of rammed earth, while the sections near Beijing are of stones and bricks. Badaling, the section of Great Wall north of Juyong Pass more than 1,000 m above sea level, was built with stone blocks and large bricks. Averaging 7.8 m in height, the wall measures 6.5 m wide at the base and 5.8 m at the top, enough for five horses or ten persons to march in a row . On top of the wall are parapets, buttresses, and holes for observation and shooting. At intervals of several hundred meters are watchtowers and beacon towers.

    The watchtower can station several dozen soldiers, and the beacon tower is where a signal fire is lit to transmit information. There are about 200 passes along the Great Wall, from Jiayu Pass in the west to Shanhai Pass in the east. Other famous passes include Juyong, Yanmen, and Zijing. In a section near Shanhai Pass, the Great Wall crosses a river in a valley, with nine arches in the wall to allow the flow of water. In modern times, the passes no longer serve as defense fortifications. Some of them have become thoroughfares, some have developed into cities, and others have become historic sites and tourist attractions.

    The Great Wall is the most time- and labor-consuming construction project in human history, estimated to have taken 180 million cubic meters of rammed earth and 60 million cubic meters of stones and bricks. All these materials are more than enough to build a wall that is five meters high and one meter wide around the globe. To build such a gigantic structure in the mountains, one can hardly imagine how the sites were surveyed, how the wall and other facilities were designed and built, where the materials were obtained, how they were transported to the sites, and how the contingents of construction workers got their supplies.