Great Wall of China

The Great Wall of China is a massive system of walls, towers and fortifications built along China's northern border to defend against invasions from the north. Stretching 13,000 miles, the Wall is one of the most recognizable structures in the world. Built over 2,000 years ago, the Great Wall's architectural history is a fascinating story of human ingenuity and engineering.

The earliest version of the Great Wall was built in the 7th century BC. Built in the Warring States Period. At that time, the city wall was made of earth and wood, and it was built to resist the attacks of nomadic tribes. The Wall is not continuous but consists of separate fortifications built by different countries to protect their borders.

• During the Qin Dynasty (221-206 BC), China's first emperor, Qin Shi Huang, ordered the construction of a unified city wall and fortification system along China's northern border. The wall was built using rammed earth, a technique in which layers of soil are compacted into a strong structure. The wall was built by conscripts who worked in difficult conditions and suffered many casualties. The wall was completed in just 10 years and is more than 3,000 miles long.

• The Han Dynasty (206 BC - 220 AD) further expanded the Great Wall, extending it westward to the Gobi Desert. During this period, bricks and stones were used to strengthen the city wall, and watchtowers and barracks were added to improve the defense capability.

• The Sui Dynasty (581-618 AD) continued to expand the walls, using bricks and tiles. The Tang Dynasty (618-907 AD) further fortified the city walls, building forts and watchtowers along its length.

• During the Ming Dynasty (1368-1644 AD), the Great Wall was extensively repaired and expanded. The Ming Dynasty reinforced the city wall with bricks and stones, and added battlements, watchtowers, and fortresses. The walls were also equipped with cannons and other firearms to enhance their defenses.

In modern times, the Great Wall has been repaired and protected. Many sections of the Great Wall have been rebuilt and maintained for tourism, and the Great Wall is now one of China's most popular tourist attractions.

The architectural history of the Great Wall has witnessed the ingenuity and perseverance of the Chinese people. Built over a period of more than 2,000 years, the Wall required an incredible feat of engineering and labor to build it. Today, the Great Wall is a symbol of China's rich cultural heritage and a testimony to the country's long and turbulent history.