Great Wall Of China

Do You Know? the only thing visible on the earth from the moon would be the Great Wall of China.

The Great Wall of China is a series of stone and earthen fortifications in , built, rebuilt, and maintained between the 5th century BC and the 16th century to protect the northern borders of the Chinese Empire during the rule of successive dynasties. Several walls, referred to as the Great Wall of China , were built since the 5th century BC. The most famous is the wall built between 220 BC and 200 BC by the first Emperor of China, Qin Shi Huang; little of it remains; it was much farther north than the current wall, which was built during the Ming Dynasty.

The Great Wall is the world's longest human-made structure, stretching over approximately 6,400 km (4,000 miles) from Shanhaiguan in the east to Lop Nur in the west, along an arc that roughly delineates the southern edge of Inner Mongolia, but stretches to over 6,700 km (4,160 miles) in total. It is also the largest human-made structure ever built in terms of surface area and mass. At its peak the Ming Wall was guarded by more than one million men. It has been estimated that somewhere in the range of 2 to 3 million Chinese died as part of the centuries-long project of building the wall. 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. 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. 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)

In 221 BC, the Emperor Qin absorbed the other six states and set up the first unified kingdom in Chinese history. In order to strengthen his newly born authority and defend the Huns in the north, he ordered connecting the walls once built by the other states as well as adding some sections of his own. Thus was formed the long Qin's Great Wall which started from the east of today's Liaoning Province and ended at Lintao, Gansu Province. In the Western Han Dynasty, the Huns became more powerful. The Han court started to build more walls on a larger scale in order to consolidate the frontier. In the west, the wall along the Hexi corridor, Yumenguan Pass, and Yangguan Pass was built. In the north, Yanmenguan Pass and Niangziguan Pass in Shanxi were set up. Many more sections of the wall extended to Yinshan Mountain and half of the ancient Silk Road was along the Han's wall. The Northern Wei, Northern Qi and Northern Zhou Dynasties all built their own sections but on a smaller scale than the walls in the Han Dynasty. The powerful Tang Dynasty saw peace between the northern tribes and central China most of the time, so few Great Wall sections were built in this period

The Ming Dynasty is the peak of wall building in Chinese history. The Ming suffered a lot by disturbances from minority tribes such as the Dadan, Tufan and Nuzhen. The Ming court from its first emperor to the last ceaselessly built walls in the north. The main line started from Jiuliancheng near the Yalu River in the east to the Jiayuguan Pass in the west and measured over 4,600 miles. Besides adding many more miles of its own, the Ming emperors ordered enlargement of the walls of previous dynasties into double-line or multi-line walls. For example, out of Yanmenguan Pass were added three big stone walls and 23 small stone walls. Eleven Garrisons were distributed along the main line of the wall. The countless walls, fortresses, and watch towers made the country strongly fortified. In the early Qing Dynasty, some sections of the walls were repaired and several sections were extended. This great engineering work stopped in the middle of the Qing Dynasty.

The most comprehensive archaeological survey, using advanced technologies, has concluded that all the walls measure 8,851.8 km (5,500.3 mi). This is made up of 6,259.6 km (3,889.5 mi) sections of actual wall, 359.7 km (223.5 mi) of trenches and 2,232.5 km (1,387.2 mi) of natural defensive barriers such as hills and rivers