Great Wall of China - Facts & Summary - HISTORY.com Great Wall of China A+E Networks Introduction Perhaps the most recognizable symbol of China and its long and vivid history, the Great Wall of China actually consists of numerous walls and fortifications, many running parallel to each other. Originally conceived by Emperor Qin Shi Huang (c. 259-210 B.C.) in the third century B.C. as a means of preventing incursions from barbarian nomads into the Chinese Empire, the wall is one of the most extensive construction projects ever completed. The best-known and best-preserved section of the Great Wall was built in the 14th through 17th centuries A.D., during the Ming dynasty (1368-1644). Though the Great Wall never effectively prevented invaders from entering China, it came to function more as a psychological barrier between Chinese civilization and the world, and remains a powerful symbol of the country’s enduring strength. Google Qin Dynasty Construction Though the beginning of the Great Wall of China can be traced to the third century B.C., many of the fortifications included in the wall date from hundreds of years earlier, when China was divided into a number of individual kingdoms during the so-called Warring States Period.

Around 220 B.C., Qin Shi Huang, the first emperor of a unified China, ordered that earlier fortifications between states be removed and a number of existing walls along the northern border be joined into a single system that would extend for more than 10,000 li (a li is about one-third of a mile) and protect China against attacks from the north. Did You Know? When Emperor Qin Shi Huang ordered construction of the Great Wall around 221 B.C., the labor force that built the wall was made up largely of soldiers and convicts. It is said that as many as 400,000 people died during the wall's construction; many of these workers were buried within the wall itself. Construction of the “Wan Li Chang Cheng,” or 10,000-Li-Long Wall, was one of the most ambitious building projects ever undertaken by any civilization. The famous Chinese general Meng Tian directed the project, and was said to have used a massive army of soldiers, convicts and commoners as workers. Made mostly of earth and stone, the wall stretched from the China Sea port of Shanhaiguan over 3,000 miles west into Gansu province.

In some strategic areas, sections of the wall overlapped for maximum security (including the Badaling stretch, north of Beijing, that was later restored by the Ming dynasty). From a base of 15 to 50 feet, the Great Wall rose some 15-30 feet high and was topped by ramparts 12 feet or higher; guard towers were distributed at intervals along it. The Great Wall of China Through the Centuries With the death of Qin Shi Huang and the fall of the Qin dynasty, much of the Great Wall fell into disrepair. After the fall of the Han dynasty (206 B.C.-220 A.D.), a series of frontier tribes seized control in northern China. The most powerful of these was the Northern Wei dynasty (386-535 A.D.), which repaired and extended the existing wall to defend against attacks from other tribes. The Bei Qi kingdom (550–577) built or repaired more than 900 miles of wall, and the short-lived but effective Sui dynasty (581–618) repaired and extended the Great Wall of China a number of times.

With the fall of the Sui and the rise of the Tang dynasty (618-907), the Great Wall lost its importance as a fortification, as China had defeated the Tujue tribe to the north and expanded past the original frontier protected by the wall. During the Song dynasty (960-1279), the Chinese were forced to withdraw under threat from the Liao and Jin peoples to the north, who took over many areas on both sides of the Great Wall. The powerful Yuan (Mongol) dynasty (1206-1368) established by Genghis Khan eventually controlled all of China, parts of Asia and sections of Europe. Though the Great Wall held little importance for the Mongols as a military fortification, soldiers were assigned to man the wall in order to protect merchants and caravans traveling along the profitable trade routes established during this period. Wall Building During the Ming Dynasty Despite its long history, the Great Wall of China as it is exists today was constructed mainly during the mighty Ming dynasty (1368-1644).

Like the Mongols, the early Ming rulers had little interest in building border fortifications, and wall building was limited before the late 15th century. In 1421, the Ming emperor Yongle proclaimed China’s new capital, Beijing, on the site of the former Mongol city of Dadu. Under the strong hand of the Ming rulers, Chinese culture flourished, and the period saw an immense amount of construction in addition to the Great Wall, including bridges, temples and pagodas. The construction of the Great Wall as it is known today began around 1474. After an initial phase of territorial expansion, Ming rulers took a largely defensive stance, and their reformation and extension of the Great Wall was key to this strategy. The Ming wall extended from the Yalu River in Liaoning Province to the eastern bank of the Taolai River in Gansu Province, and winded its way from east to west through today’s Liaoning, Hebei, Tianjin, Beijing, Inner Mongolia, Shanxi, Shaanxi, Ningxia and Gansu. Starting west of Juyong Pass, the Great Wall was split into south and north lines, respectively named the Inner and Outer Walls.

Strategic “passes” (i.e., fortresses) and gates were placed along the wall; the Juyong, Daoma and Zijing passes, closest to Beijing, were named the Three Inner Passes, while further west were Yanmen, Ningwu and Piantou, the Three Outer Passes. All six passes were heavily garrisoned during the Ming period and considered vital to the defense of the capital. Significance of the Great Wall of China In the mid-17th century, the Manchus from central and southern Manchuria broke through the Great Wall and encroached on Beijing, eventually forcing the fall of the Ming dynasty and beginning of the Qing (Manchu) dynasty (1644-1912). Between the 18th and 20th centuries, the Great Wall emerged as the most common emblem of China for the Western world, and a symbol both physical–a manifestation of Chinese strength–and psychological–a representation of the barrier maintained by the Chinese state to repel foreign influences and exert control over its citizens. Today, the Great Wall is generally recognized as one of the most impressive architectural feats in history.

In 1987, UNESCO designated the Great Wall a World Heritage site, and a popular claim that emerged in the 20th century holds that it is the only manmade structure that is visible from the moon. Over the years, roadways have been cut through the wall in various points, and many sections have deteriorated after centuries of neglect. The best-known section of the Great Wall of China–Badaling, located 43 miles (70 km) northwest of Beijing–was rebuilt in the late 1950s, and attracts thousands of national and foreign tourists every day. Tags Great Wall of China | wall, China | Britannica.com Great Wall of China Alternative Titles: Wan-li Ch’ang-ch’eng, Wanli Changcheng Related Topics Meng Tian Great Wall of China, Chinese (Pinyin) Wanli Changcheng or (Wade-Giles romanization) Wan-li Ch’ang-ch’eng (“10,000-Li Long Wall”), extensive bulwark erected in ancient China , one of the largest building-construction projects ever undertaken. The Great Wall actually consists of numerous walls—many of them parallel to each other—built over some two millennia across northern China and southern Mongolia .

The most extensive and best-preserved version of the wall dates from the Ming dynasty (1368–1644) and runs for some 5,500 miles (8,850 km) east to west from Mount Hu near Dandong , southeastern Liaoning province, to Jiayu Pass west of Jiuquan , northwestern Gansu province. This wall often traces the crestlines of hills and mountains as it snakes across the Chinese countryside, and about one-fourth of its length consists solely of natural barriers such as rivers and mountain ridges. Nearly all of the rest (about 70 percent of the total length) is actual constructed wall, with the small remaining stretches constituting ditches or moats. Although lengthy sections of the wall are now in ruins or have disappeared completely, it is still one of the more remarkable structures on Earth . The Great Wall was designated a UNESCO World Heritage site in 1987. Great Wall of China, near Beijing. © Digital Vision/Getty Images Great Wall of China, eastern Asia, designated a World Heritage site in 1987. Overview of the Great Wall of China.

Contunico © ZDF Enterprises GmbH, Mainz Large parts of the fortification system date from the 7th through the 4th century bce. In the 3rd century bce Shihuangdi (Qin Shihuang), the first emperor of a united China (under the Qin dynasty), connected a number of existing defensive walls into a single system. Traditionally, the eastern terminus of the wall was considered to be Shanhai Pass ( Shanhaiguan ) in eastern Hebei province along the coast of the Bo Hai (Gulf of Chihli), and the wall’s length—without its branches and other secondary sections—was thought to extend for some 4,160 miles (6,700 km). However, government-sponsored investigations that began in the 1990s revealed sections of wall in Liaoning, and aerial and satellite surveillance eventually proved that this wall stretched continuously through much of the province. The greater total length of the Ming wall was announced in 2009. The Great Wall of China at Shanhaiguan, Hebei province, China. Daniel Ng Bank of China Tower The Great Wall developed from the disparate border fortifications and castles of individual Chinese kingdoms.

For several centuries these kingdoms probably were as concerned with protection from their near neighbours as they were with the threat of barbarian invasions or raids. Early building About the 7th century bce the state of Chu started to construct a permanent defensive system. Known as the “Square Wall,” this fortification was situated in the northern part of the kingdom’s capital province. From the 6th to the 4th century other states followed Chu’s example. In the southern part of the Qi state an extensive perimeter wall was gradually created using existing river dikes, newly constructed bulwarks , and areas of impassable mountain terrain. The Qi wall was made mainly of earth and stone and terminated at the shores of the Yellow Sea . In the Zhongshan state a wall system was built to thwart invasion from the states of Zhao and Qin in the southwest. There were two defensive lines in the Wei state: the Hexi (“West of the [ Yellow ] River”) and Henan (“South of the River”) walls. The Hexi Wall was a fortification against the Qin state and western nomads.

Built during the reign of King Hui (370–335 bce), it was expanded from the dikes on the Luo River on the western border. It started in the south near Xiangyuan Cave, east of Mount Hua, and ended at Guyang in what is now the Inner Mongolia Autonomous Region. Henan Wall, built to protect Daliang (the capital, now Kaifeng ), was repaired and extended in King Hui’s later years. The Zheng state also built a wall system, which was rebuilt by the Han state after it conquered Zheng. The state of Zhao completed a southern wall and a northern wall; the southern wall was built mainly as a defense against the Wei state. Moon rising (left background) over the Great Wall of China. © Paul Merrett/Shutterstock.com Ringling Bros. Folds Its Tent After administrative reorganization was carried out by Shang Yang (died 338 bce), the Qin state grew politically and militarily to become the strongest among the seven states, but it was frequently raided by the Donghu and Loufan, two nomadic peoples from the north.

Therefore, the Qin erected a wall that started from Lintiao, went north along the Liupan Mountains , and ended at the Huang He (Yellow River). All About Asia In the Yan state two separate defensive lines were prepared—the Northern Wall and the Yishui Wall—in an effort to defend the kingdom from attacks by northern groups such as the Donghu, Linhu, and Loufan, as well as by the Qi state in the south. The Yishui Wall was expanded from the dike of the Yi River as a defense line against Qi and Zhao, its two main rival states. It began southwest of Yi City, the capital, and ended south of Wen’an. In 290 bce the Yan state built the Northern Wall along the Yan Mountains, starting from the northeast in the area of Zhangjiakou in Hebei , passing over the Liao River , and extending to the ancient city of Xiangping (modern Liaoyang ). This was the last segment of the Great Wall to be erected during the Zhanguo ( Warring States ) period. In 221 bce Shihuangdi , the first Qin emperor, completed his annexation of Qi and thus unified China.

He ordered removal of the fortifications set up between the previous states because they served only as obstacles to internal movements and administration. In addition, he sent Gen. Meng Tian to garrison the northern border against incursions of the nomadic Xiongnu and to link the existing wall segments in Qin, Yan, and Zhao into the so-called “10,000-Li Long Wall” (2 li equal approximately 0.6 mile [1 km]). This period of construction began about 214 bce and lasted a decade. Hundreds of thousands of soldiers and conscripted workers laboured on the project. With the fall of the Qin dynasty after Shihuangdi’s death, however, the wall was left largely ungarrisoned and fell into disrepair. Great Wall of China at Mutianyu, northeast of Beijing. © Ron Gatepain (A Britannica Publishing Partner) The Han through Yuan dynasties Connect with Britannica Facebook Twitter YouTube Instagram Pinterest During the reign of the Han emperor Wudi (141–87 bce), the wall was strengthened as part of an overall campaign against the Xiongnu.

From that period the Great Wall also contributed to the exploitation of farmland in northern and western China and to the growth of the trade route that came to be known as the Silk Road . In 121 bce a 20-year project of construction was started on the Hexi Wall (generally known as the Side Wall) between Yongdeng (now in Gansu ) in the east and Lake Lop Nur (now in Xinjiang) in the west. According to Juyan Hanjian (“Juyan Correspondence of the Han”), the strongpoints set up along the wall included “a beacon every 5 li, a tower every 10 li, a fort every 30 li, and a castle every 100 li.” The main work on the wall during the Dong (Eastern) Han period (25–220 ce) took place during the reign of Liu Xiu ( Guangwudi ), who in 38 ordered the repair of four parallel lines of the Great Wall in the area south of the Hexi Wall. The Great Wall served not only for defense but also to centralize control of trade and travel.

During the Bei (Northern) Wei dynasty (386–534/535 ce), the Great Wall was repaired and extended as a defense against attacks from the Juan-juan and Khitan tribes in the north. According to Wei shu: Mingyuandi Ji (“History of Wei: Chronicle of Emperor Mingyuan”), in 417, the eighth year of the reign of Mingyuandi (409–423), a part of the Great Wall was built south of Changchuan, from Chicheng (now in Hebei) to Wuyuan (now in Inner Mongolia ) in the west, extending more than 620 miles (1,000 km). During the reign of Taiwudi (423–452), a lower and thinner wall of rammed earth was built around the capital as a complement to the Great Wall. Starting from Guangling in the east, it extended to the eastern side of the Huang He, forming a circle around Datong . In 549, after the Dong Wei kingdom moved its capital east to Ye, it also built a segment of the Great Wall in the area of contemporary Shanxi province.

A portion of the Great Wall of China near Qinhuangdao, Hebei province, northeastern China. © qhdcrq/Shutterstock.com Editor Picks: Exploring 10 Types of Basketball Movies In order to strengthen its northern frontier and prevent invasion from the west by the Bei Zhou, the Bei Qi kingdom (550–577) launched several big construction projects that were nearly as extensive in scope as the building projects of the Qin dynasty. In 552 a segment was built on the northwestern border, and only three years later the emperor ordered the recruitment of 1.8 million workers to repair and extend other sections. The construction took place between the south entrance of Juyong Pass (near modern Beijing ) and Datong (in Shanxi). In 556 a new fortification was set up in the east and extended to the Yellow Sea. The following year a second wall was built inside the Great Wall within modern Shanxi, beginning in the vicinity of Laoying east of Pianguan, extending to the east beyond Yanmen Pass and Pingxing Pass, and ending in the area around Xiaguan in Shanxi.

In 563 the emperor Wuchengdi of the Bei Qi had a segment repaired along the Taihang Mountains . That is the part of the Great Wall found today in the area around Longguan, Guangchang, and Fuping (in Shanxi and Hebei). In 565 the inner wall built in 557 was repaired, and a new wall was added that started in the vicinity of Xiaguan, extended to the Juyong Pass in the east, and then joined to the outer wall. The segments repaired and added during the Bei Qi period totaled some 900 miles (1,500 km), and towns and barracks were established at periodic intervals to garrison the new sections. In 579, in order to prevent invasions of the Bei Zhou kingdom by the Tujue (a group of eastern Turks) and the Khitan, the emperor Jing started a massive rebuilding program on areas of the wall located in the former Bei Qi kingdom, starting at Yanmen in the west and ending at Jieshi in the east. Great Wall of China at Juyong Pass.

Dennis Jarvis (CC-BY-2.0) (A Britannica Publishing Partner) Trending Topics Eyjafjallajökull volcano During the Sui dynasty (581–618) the Great Wall was repaired and improved seven times in an effort to defend the country against attacks from the Tujue. After the Tang dynasty (618–907) replaced the Sui, the country grew much stronger militarily, defeating the Tujue in the north and expanding beyond the original frontier. Thus, the Great Wall gradually lost its significance as a fortification, and there was no need for repairs or additions. During the Song dynasty (960–1279), however, the Liao and Jin peoples in the north were a constant threat. The Song rulers were forced to withdraw to the south of the lines of the Great Wall built by the Qin, Han, and Northern dynasties . Many areas on both sides of the wall were subsequently taken over by the Liao (907–1125) and Jin dynasties (1115–1234).

When the Song rulers had to retreat even farther—to the south of the Yangtze River (Chang Jiang)—repairs to the wall or extensions of it were no longer feasible . Limited repairs were carried out once (1056) during Liao times but only in the area between the Yazi and Huntong rivers. Time-lapse photograph of a meteor shower over the Great Wall of China at Badaling Pass. Stephen Shaver—AFP/Getty Images In 1115, after the Jin dynasty was established, work was performed on two defensive lines at Mingchang. The old wall there—previously called the Wushu Wall, or Jinyuan Fort—ran westward from a point north of Wulanhada, then wound through the Hailatu Mountains, turning to the north and then to the west again, finally ending at the Nuanshui River. The second of the lines was the new Mingchang Wall, also called the Inner Jin Wall or the Jin Trench, which was constructed south of the old wall. It started in the west from a bend in the Huang He and ended at the Sungari (Songhua) River .

During the Yuan (Mongol) dynasty (1206–1368), the Mongols controlled all of China, as well as other parts of Asia and sections of Europe . As a defensive structure the Great Wall was of little significance to them; however, some forts and key areas were repaired and garrisoned in order to control commerce and to limit the threat of rebellions from the Chinese (Han) and other nationalities. The Ming dynasty to the present Rulers during the Ming dynasty (1368–1644) ceaselessly maintained and strengthened the Great Wall to prevent another Mongolian invasion. The majority of the work took place along the old walls built by the Bei Qi and Bei Wei. The western limit of the Great Wall of China viewed from a Ming fortress (1372), near Jiuquan, … Wolfgang Kaehler Most of the Great Wall that stands today is the result of work done during the reign of the Hongzhi emperor (1487–1505). Starting west of Juyong Pass, this part of the wall was split into south and north lines, respectively named the Inner and Outer walls.

Along the wall were many strategic “passes” (i.e., fortresses) and gates. Among them were Juyong, Daoma, and Zijing passes, the three closest to the Ming capital Beijing. Together they were referred to as the Three Inner Passes. Farther west were Yanmen, Ningwu, and Piantou passes, known as the Three Outer Passes. Both the Inner and Outer passes were of key importance in protecting the capital and were usually heavily garrisoned. Tourists on a section of the Great Wall of China near Beijing. © Marius Hetrea After the Qing (Manchu) dynasty (1644–1911/12) replaced the Ming, there was a change in ruling strategy called huairou (“mollification”), wherein the Qing tried to pacify the leaders and peoples of Mongolia, Tibet, and other nationalities by not interfering with local social, cultural, or religious life. Because of the success of that strategy, the Great Wall was repaired less frequently, and it gradually fell into ruin. Design of the fortifications The Great Wall had three major components: passes, signal towers (beacons), and walls.

Passes Passes were major strongholds along the wall, usually located at such key positions as intersections with trade routes. The ramparts of many passes were faced with huge bricks and stones, with dirt and crushed stones as filler. The bastions measured some 30 feet (10 metres) high and 13 to 16 feet (4 to 5 metres) wide at the top. Within each pass were access ramps for horses and ladders for soldiers. The outside parapet was crenellated, and the inside parapet, or yuqiang (nüqiang), was a low wall about 3 feet (1 metre) high that prevented people and horses from falling off the top. In addition to serving as an access point for merchants and other civilians, the gate within the pass was used as an exit for the garrison to counterattack raiders or to send out patrols. Under the gate arch there was typically a huge double door of wood. Bolts and locker rings were set in the inner panel of each door. On top of each gate was a gate tower that served as a watchtower and command post.

Usually it stood one to three stories (levels) high and was constructed either of wood or of bricks and wood. Built outside the gate, where an enemy was most likely to attack, was a wengcheng, a semicircular or polygonal parapet that shielded the gate from direct assault. Extending beyond the most strategic wengchengs was an additional line of protection, the luocheng, which was often topped by a tower used to watch those beyond the wall and to direct troop movements in battles waged there. Around the gate entrance there was often a moat that was formed in the process of digging earth to build the fortifications. Westernmost portion of the Great Wall of China at Jiayu Pass, near Jiuquan, Gansu province; a Ming … iStockphoto/Thinkstock Signal towers Signal towers were also called beacons, beacon terraces, smoke mounds, mounds, or kiosks. They were used to send military communications : beacon (fires or lanterns) during the night or smoke signals in the daytime; other methods such as raising banners, beating clappers, or firing guns were also used.

Signal towers, often built on hilltops for maximum visibility, were self-contained high platforms or towers. The lower levels contained rooms for soldiers, as well as stables, sheepfolds, and storage areas. Walls The wall itself was the key part of the defensive system. It usually stood 21.3 feet (6.5 metres) wide at the base and 19 feet (5.8 metres) at the top, with an average height of 23 to 26 feet (7 to 8 metres), or a bit lower on steep hills. The structure of the wall varied from place to place, depending on the availability of building materials. Walls were made of tamped earth sandwiched between wooden boards, adobe bricks, a brick and stone mixture, rocks, or pilings and planks. Some sections made use of existing river dikes; others used rugged mountain terrain such as cliffs and gorges to take the place of man-made structures. Great Wall of China.

© Izmael/Shutterstock.com In the western deserts the walls were often simple structures of rammed earth and adobe; many eastern ramparts, such as those near Badaling, were faced with stone and included a number of secondary structures and devices. On the inner side of such walls, placed at small intervals, were arched doors called juan, which were made of bricks or stones. Inside each juan were stone or brick steps leading to the top of the battlement . On the top, on the side facing outward, stood 7-foot- (2-metre-) high crenels called duokou. On the upper part of the duokou were large openings used to watch and shoot at attackers, and on the lower part were small openings, or loopholes, through which defenders could also shoot. At intervals of about 650 to 1,000 feet (200 to 300 metres) there was a crenellated platform rising slightly above the top of the wall and protruding from the side that faced attackers. During battle the platform provided a commanding view and made it possible to shoot attackers from the side as they attempted to scale the wall with ladders.

On several platforms were simply structured huts called pufang, which provided shelter for the guards during storms. Some platforms, as with signal towers, had two or three stories and could be used to store weapons and ammunition. Those at Badaling commonly had two stories, with accommodations for more than 10 soldiers on the lower level. There were also drainage ditches on the walls to shield them from damage by excessive rainwater. Military administration Each major stronghold along the wall was hierarchically linked to a network of military and administrative commands. During the rule of Shihuangdi, 12 prefectures were established along the wall, and in the Ming period the whole fortification was divided into 9 defense areas, or zones. A post chief (zongbingguan) was assigned to each zone. Together they were known as the Nine Border Garrisons. Tradition and conservation The Great Wall has long been incorporated into Chinese mythology and popular symbolism , and in the 20th century it came to be regarded as a national symbol.

Above the East Gate (Dongmen) at Shanhai Pass is an inscription attributed to the medieval historian Xiao Xian, which is translated as “First Pass Under Heaven,” referring to the traditional division between Chinese civilization and the barbarian lands to the north. Rebuilt section of the Great Wall of China near Simatai, northeast of Beijing. © Mikhail Nekrasov/Shutterstock.com Despite the wall’s cultural significance, roadways have been cut through it at several points, and vast sections have suffered centuries of neglect. In the 1970s a segment near Simatai (68 miles [110 km] northeast of Beijing) was dismantled for building materials, but it was subsequently rebuilt. Other areas have also been restored, including just northwest of Jiayu Pass at the western limit of the wall; at Huangya Pass, some 105 miles (170 km) north of Tianjin ; and at Mutianyu, about 55 miles (90 km) northeast of Beijing.

The best-known section, at Badaling (43 miles [70 km] northwest of Beijing), was rebuilt in the late 1950s; it now attracts thousands of national and foreign tourists every day. Portions of the wall around Shanhai Pass and at Mount Hu, the eastern terminus, also had been rebuilt by 2000. Watchtower on the Great Wall of China at Mutianyu, northeast of Beijing. © Ron Gatepain (A Britannica Publishing Partner) Additional Media The Great Wall of China - Crystalinks The Great Wall of China The Great Wall of China is a series of fortifications made of stone, brick, tamped earth, wood, and other materials, generally built along an east-to-west line across the historical northern borders of China in part to protect the Chinese Empire or its prototypical states against intrusions by various nomadic groups or military incursions by various warlike peoples or forces. It is included in lists of the "Seven Medieval Wonders of the World" but was of course not one of the classical Seven Wonders of the World recognized by the ancient Greeks. The Wall was made a UNESCO World Heritage Site in 1987.

Condition Fears raised as 'one third' of China's Great Wall disappears CNN - July 2, 2015 It was originally built to defend an empire, but now parts of the Great Wall of China are crumbling so badly they need someone to leap to their defense. About 2,000 kilometers, or 30%, of the ancient fortification built in the Ming Dynasty era has disappeared due to natural erosion and human damage, according to the Beijing Times. While some portions north of Beijing and near tourist centers have been preserved and even reconstructed, in many locations the Wall is in disrepair. Those parts might serve as a village playground or a source of stones to rebuild houses and roads. Sections of the Wall are also prone to graffiti and vandalism. Parts have been destroyed because the Wall is in the way of construction. No comprehensive survey of the wall has been carried out, so it is not possible to say how much of it survives, especially in remote areas. Intact or repaired portions of the Wall near developed tourist areas are often frequented by sellers of tourist kitsch.

More than 60 kilometres (37 mi) of the wall in Gansu province may disappear in the next 20 years, due to erosion from sandstorms. In places, the height of the wall has been reduced from more than five meters (16.4 ft) to less than two meters. The square lookout towers that characterize the most famous images of the wall have disappeared completely. Many western sections of the wall are constructed from mud, rather than brick and stone, and thus are more susceptible to erosion. The materials used are those available near the site of construction. Near Beijing the wall is constructed from quarried limestone blocks. In other locations it may be quarried granite or fired brick. Where such materials are used, two finished walls are erected with earth and rubble fill placed in between with a final paving to form a single unit. In some areas the blocks were cemented with a mixture of glutinous rice and egg-white. In the extreme western desert locations, where good materials are scarce, the wall was constructed from dirt rammed between rough wood tied together with woven mats.

Size The Great Wall is the world's longest human-made structure stretching from Shanhaiguan in the east, to Lop Lake in the west, along an arc that roughly delineates the southern edge of Inner Mongolia. A comprehensive archaeological survey, using advanced technologies, has concluded that the Ming walls measure 8,850 km (5,500 mi). This is made up of 6,259 km (3,889 mi) sections of actual wall, 359 km (223 mi) of trenches and 2,232 km (1,387 mi) of natural defensive barriers such as hills and rivers. Another archaeological survey found that the entire wall with all of its branches measure out to be 21,196 km (13,171 mi).

Great Wall of China more than twice as long as previous estimates MSNBC - June 10, 2012 According to a recent BBC News report, the wall, which is a series of fortifications made of stone, brick and rammed earth, was subject to a recent archaeological survey that found its total length to be 21,196 km or 13,171 miles. Based on a 2009 study, it was thought to be much shorter at 8,850 km. The Great Wall, which was built in 500 BC to protect China's northern border, is the world's largest manmade structure. The Great Wall of China has been officially declared even longer than previously thought, state-run media report. The wall measures 21,196.18km (13,170.6956 miles) long based on the latest state survey results, state-run news agency Xinhua reported today. History The first major wall was built during the reign of the First Emperor, the main emperor of the short-lived Qin dynasty.

This wall was not constructed as a single endeavor, but rather was created by the joining of several regional walls built by the Warring States. It was located much further north than the current Great Wall, and very little remains of it. A defensive wall on the northern border was built and maintained by several dynasties at different times in Chinese history. Several walls were being built as early as the 7th century BC; these, later joined together and made bigger, stronger, and unified are now collectively referred to as the Great Wall. Especially famous is the wall built between 220-206 BC by the first Emperor of China, Qin Shi Huang. Little of that wall remains. Since then, the Great Wall has on and off been rebuilt, maintained, enhanced; the majority of the existing wall was reconstructed during the Ming Dynasty. The Great Wall that can still be seen today was built during the Ming Dynasty, on a much larger scale and with longer lasting materials (solid stone used for the sides and the top of the Wall) than any wall that had been built before.

The primary purpose of the wall was not to keep out people, who could scale the wall, but to insure that semi-nomadic people on the outside of the wall could not cross with their horses or return easily with stolen property. Other purposes of the Great Wall have included border controls, allowing the imposition of duties on goods transported along the Silk Road, regulation or encouragement of trade and the control of immigration and emigration. Furthermore, the defensive characteristics of the Great Wall were enhanced by the construction of watch towers, troop barracks, garrison stations, signaling capabilities through the means of smoke or fire, and the fact that the path of the Great Wall also served as a transportation corridor. There have been four major walls: 208 BC (the Qin Dynasty) 1st century BC (the Han Dynasty) 1138 - 1198 (the Five Dynasties and Ten Kingdoms Period) 1368-1620 (from Hongwu Emperor until Wanli Emperor of the Ming Dynasty) The Chinese were already familiar with the techniques of wall-building by the time of the Spring and Autumn Period, which began around the 7th century BC.

During the Warring States Period from the 5th century BC to 221 BC, the states of Qi, Yan and Zhao all constructed extensive fortifications to defend their own borders. Built to withstand the attack of small arms such as swords and spears, these walls were made mostly by stamping earth and gravel between board frames. Qin Shi Huang conquered all opposing states and unified China in 221 BC, establishing the Qin Dynasty. Intending to impose centralized rule and prevent the resurgence of feudal lords, he ordered the destruction of the wall sections that divided his empire along the former state borders. To protect the empire against intrusions by the Xiongnu people from the north, he ordered the building of a new wall to connect the remaining fortifications along the empire's new northern frontier. Transporting the large quantity of materials required for construction was difficult, so builders always tried to use local resources. Stones from the mountains were used over mountain ranges, while rammed earth was used for construction in the plains. The peasants who died working were buried inside the wall, to be unearthed later by archaeologists. There are no surviving historical records indicating the exact length and course of the Qin Dynasty walls.

Most of the ancient walls have eroded away over the centuries, and very few sections remain today. Possibly as many as one million people died building the Wall under the Qin Dynasty. Later, the Han, Sui, Northern and Jin dynasties all repaired, rebuilt, or expanded sections of the Great Wall at great cost to defend themselves against northern invaders. The Great Wall concept was revived again during the Ming Dynasty following the Ming army's defeat by the Oirats in the Battle of Tumu in 1449. The Ming had failed to gain a clear upper-hand over the Mongols after successive battles, and the long-drawn conflict was taking a toll on the empire. The Ming adopted a new strategy to keep the nomadic Mongols out by constructing walls along the northern border of China. Acknowledging the Mongol control established in the Ordos Desert, the wall followed the desert's southern edge instead of incorporating the bend of the Huang He. Unlike the earlier Qin fortifications, the Ming construction was stronger and more elaborate due to the use of bricks and stone instead of rammed earth. As Mongol raids continued periodically over the years, the Ming devoted considerable resources to repair and reinforce the walls.

Sections near the Ming capital of Beijing were especially strong. Towards the end of the Shun Dynasty, the Great Wall helped defend the empire against the Manchu invasions that began around 1600. Under the military command of Yuan Chonghuan, the Ming army held off the Manchus at the heavily fortified Shanhaiguan pass, preventing the Manchus from entering the Liaodong Peninsula and the Chinese heartland. The Manchus were finally able to cross the Great Wall in 1644, when the gates at Shanhaiguan were opened by Wu Sangui, a Ming border general who disliked the activities of rulers of the Shun Dynasty. The Manchus quickly seized Beijing, and defeated the newly founded Shun Dynasty and remaining Ming resistance, to establish the Qing Dynasty. Under Qing rule, China's borders extended beyond the walls and Mongolia was annexed into the empire, so construction and repairs on the Great Wall were discontinued. A counterpart wall to the Great Wall in the south was erected to protect and divide the Chinese from the 'southern barbarians' called Miao (meaning barbaric and nomadic). Before the use of bricks, the Great Wall was mainly built from earth, stones, and wood.

During the Ming Dynasty, however, bricks were heavily used in many areas of the wall, as were materials such as tiles, lime, and stone. The size and weight of the bricks made them easier to work with than earth and stone, so construction quickened. Additionally, bricks could bear more weight and endure better than rammed earth. Stone can hold under its own weight better than brick, but is more difficult to use. Consequently, stones cut in rectangular shapes were used for the foundation, inner and outer brims, and gateways of the wall. Battlements line the uppermost portion of the vast majority of the wall, with defensive gaps a little over 30 cm (one foot) tall, and about 23 cm (9 inches) wide. The steps that form the Great Wall of China are very steep and tall in some areas. Tourists often become exhausted climbing the wall and walk no more than a kilometre or two (around a mile). Notable Areas Cragged mountains from the southeast to the northwest for approximately 2.25 kilometers (about 1.3 miles). Number One Pass Under Heaven This is the first mountain the Great Wall climbs and only portion of the wall that was built as a bridge.

Badaling North Pass of Juyongguan. When used by the Chinese to protect their land, this section of the wall has had many guards to defend China's capita, Beijing. Made of stone and bricks from the hills, this portion of the Great Wall is 7.8 meters (25.6 ft) high and 5 meters (16.4 ft) wide. Ming Great Wall This is where the wall climbs extremely steep slopes. It runs 11 kilometers (7 mi) long, ranges from 5 to 8 meters (16-26 ft) in height, and 6 meters (19.7 ft) across the bottom, narrowing up to 5 meters (16.4 ft) across the top. Wangjinglou is one of Jinshanling's 67 watchtowers, 980 meters (3,215 ft)above sea level. Shanhaiguan Great Wall The "Museum of the Construction of the Great Wall", because of the Meng Jiang-Nu Temple, built during the Song Dynasty.

Visibility from Space Visibility from the Moon One of the earliest known references to this myth appears in a letter written in 1754 by the English antiquary William Stukeley. Stukeley wrote that, "This mighty wall of four score miles in length (Hadrian's Wall) is only exceeded by the Chinese Wall, which makes a considerable figure upon the terrestrial globe, and may be discerned at the moon." The claim was also mentioned by Henry Norman in 1895 where he states "besides its age it enjoys the reputation of being the only work of human hands on the globe visible from the moon." The issue of "canals" on Mars was prominent in the late 19th century and may have led to the belief that long, thin objects were visible from space. The claim that the Great Wall is visible also appears in 1932's Ripley's Believe it or Not strip and in Richard Halliburton's 1938 book Second Book of Marvels. The claim the Great Wall is visible has been debunked many times, but is still ingrained in popular culture.

The wall is a maximum 9.1 m (30 ft) wide, and is about the same color as the soil surrounding it. Based on the optics of resolving power (distance versus the width of the iris: a few millimeters for the human eye, meters for large telescopes) only an object of reasonable contrast to its surroundings which is 70 mi (110 km) or more in diameter (1 arc-minute) would be visible to the unaided eye from the moon, whose average distance from Earth is 384,393 km (238,851 mi). The apparent width of the Great Wall from the moon is the same as that of a human hair viewed from 2 miles (3.2 km) away. To see the wall from the moon would require spatial resolution 17,000 times better than normal (20/20) vision. Unsurprisingly, no lunar astronaut has ever claimed to have seen the Great Wall from the moon. Visibility from Low Earth Orbit A more controversial question is whether the Wall is visible from low earth orbit (an altitude of as little as 100 miles (160 km)).

NASA claims that it is barely visible, and only under nearly perfect conditions; it is no more conspicuous than many other man-made objects. Other authors have argued that due to limitations of the optics of the eye and the spacing of photoreceptors on the retina, it is impossible to see the wall with the naked eye, even from low orbit, and would require visual acuity of 20/3 (7.7 times better than normal). Astronaut William Pogue thought he had seen it from Skylab but discovered he was actually looking at the Grand Canal of China near Beijing. He spotted the Great Wall with binoculars, but said that "it wasn't visible to the unaided eye." U.S. Senator Jake Garn claimed to be able to see the Great Wall with the naked eye from a space shuttle orbit in the early 1980s, but his claim has been disputed by several U.S. astronauts. Veteran U.S.

astronaut Gene Cernan has stated: "At Earth orbit of 100 miles (160 km) to 200 miles (320 km) high, the Great Wall of China is, indeed, visible to the naked eye." Ed Lu, Expedition 7 Science Officer aboard the International Space Station, adds that, "it's less visible than a lot of other objects. And you have to know where to look." In 2001, Neil Armstrong stated about the view from Apollo 11: "I do not believe that, at least with my eyes, there would be any man-made object that I could see. I have not yet found somebody who has told me they've seen the Wall of China from Earth orbit. ...I've asked various people, particularly Shuttle guys, that have been many orbits around China in the daytime, and the ones I've talked to didn't see it." In October 2003, Chinese astronaut Yang Liwei stated that he had not been able to see the Great Wall of China.

In response, the European Space Agency (ESA) issued a press release reporting that from an orbit between 160 and 320 km, the Great Wall is visible to the naked eye. In an attempt to further clarify things, the ESA published a picture of a part of the �Great Wall� photographed from Space. However, in a press release a week later (no longer available in the ESA�s website), they acknowledged that the "Great Wall" in the picture was actually a river. Leroy Chiao, a Chinese-American astronaut, took a photograph from the International Space Station that shows the wall. It was so indistinct that the photographer was not certain he had actually captured it. Based on the photograph, the China Daily later reported that the Great Wall can be seen from space with the naked eye, under favorable viewing conditions, if one knows exactly where to look.[38] However, the resolution of a camera can be much higher than the human visual system, and the optics much better, rendering photographic evidence irrelevant to the issue of whether it is visible to the naked eye. Battle Forts and Watch Towers The wall is complemented by defensive fighting stations, to which wall defenders may retreat if overwhelmed.

Each tower has unique and restricted stairways and entries to confuse attackers. Barracks and administrative centers are located at larger intervals. In addition to the usual military weapons of the period, specialized wall defense weapons were used. Reproductions of weapons are displayed at the wall. Battle forts built on the summits of hills. The Mutianyu section of the Great Wall, 70 kilometers northeast of Beijing, is linked to the Gubeikou section on the east and the Badaling section on the west. It is one of the best sections of Great Wall. The Mutianyu section is crenellated for watching and shooting at the invading enemy. Some of the battle forts on the wall are as close as 50 meters apart. The Watchtower The wall also has watch towers at regular intervals, which were used to store weapons, house troops, and send smoke signals. Barracks and administrative centers are located at larger intervals. Communication between the army units along the length of the Great Wall, including the ability to call reinforcements and warn garrisons of enemy movements, was of high importance. Signal towers were built upon hill tops or other high points along the wall for their visibility.

Question: The Great Wall of China generally runs?
Answer: East-to-West