The Great Wall is China's most famous monument. It is the greatest wall ever built by man and dates to the 5th century, when rival kingdoms built walls to protect themselves. The Qin Dynasty brought the Chinese Empire together for the first time under one leader and this resulted in the fortification of the Great Wall.
Over a 10-year period, 300,000 conscripted workers, many of them slaves, worked the wall into a continuous barrier to protect the northern frontier.
The wall stretches 6350km from the Yalu River on the coast of Bohai Bay in the east to Jiayuguan Pass in the west, but the Shanhaiguan-jiayguan section is regarded as the main body.
It was constantly repositioned and extended as dynasties rose and fell. In 607 AD, more than a million labourers worked on it, but then it was largely abandoned. The Great Wall is not so much a continuous single wall, but rather a series of inner and outer walls that leave the main walls to semi-enclose strategically important areas.
It is said the Ming Great Wall is around 5000km long, but if all the walls from the earliest periods of construction are included, Chinese historians estimate the total length to be 50,000km.
About 10,000 beacon towers were built, either on the wall or on high ground as part of the system to use smoke or fire to signal the imperial capital. Much of the earlier walls were made of rammed earth and local stone and are not identified with fortresses and structure of the commonly-known Wall.
The Jinshanling section is 150km north-east of Beijing and is a small reconstructed part. It is a good example of the internationally-known Wall and was built of stone and bricks by the military garrison at Gubeikou, civilian conscripts and stonemasons.
The Great Wall at Mt Yanmen was also constructed in the Ming dynasty. It is an inner wall made of rammed earth, faced with brick and has stone-brick watchtowers. North of Datong, once enclosed by walls as the garrison town, is the outer Great Wall. The inner and outer Wall meet in the Yellow River district.
World Expeditions has tours to China, including Great Wall treks of varying lengths.