The Great Wall of China was built, rebuilt, and maintained between the 5th century BC and the 16th century. Construction on the wall began during the Zhou Dynasty, which spanned the period from 1046 to 256 BC.
Early versions of the wall have been dated back to the 7th century BC. It is believed that walls were built along the northern border of ancient Chinese cities from at least the late Spring and Autumn Period (722-481 BC). During this period, China was divided into seven separate states, who built their own independent walls for protection against barbarian invasions.
By 7th century BC, the states had united into one kingdom and the king, who was ruler of the state of Qin, began to consolidate the various walls into a single, stronger structure. This project was called the “Long Wall of Ten Thousand Li”. The wall was built from rammed earth, stones, and wood. It stretched from Lintao in the west to Liaodong in the east, where it connected with another system of walls belonging to the state of Yan.
Over the centuries, the wall was modified, strengthened and improved by successive dynasties. During the Qin Dynasty (221–206 BC), sections of the structure were reinforced with stonework, allowing it to be extended. At this point, the sections became known as the Great Wall. In addition, watchtowers were erected and garrisoned military contingents were assigned along the wall.
During the Han Dynasty (206 BC–220 AD), the Great Wall was further extended and reinforced, reaching up to 4,160 kilometres (2,590 miles) in length. Later on, during the Ming Dynasty (1368–1644), the entire structure was extended and renovated. The superstructure was made of bricks, the foundation of the Great Wall was strengthened and the height and width of the wall was increased significantly. In some parts, the wall reached up to 8 metres (26.2 feet) in depth.
The Great Wall of China has since become a symbol of endurance and strength, not only in China, but across the world. It stands as a testament to the remarkable engineering achievements of the ancient Chinese civilizations and their determination to protect themselves from invaders.