The Great Wall of China is probably our greatest building enterprise. It stretches for more than 2540 kilometres from the Gulf of Chilli on the Yellow Sea westwards to the Jade Gate to Central Asia, where the ancient silk route once passed. It was built by the emperor Huang Ti, about 200 years before the birth of Christ, to keep out the Hun horsemen of the north who were raiding his land and cities. The Emperor did not in fact have to start from scratch. He joined up sections of walls that already existed, and although he died soon after the wall was begun his successors carried on constructing for several years.

The Great Wall of China is easily accessible from Beijing, though the massive structure stretches from Shanhaiguan in the east all the way to the city of Jiayuguan, in the country’s northwest. Generally speaking, the Great Wall of China defends the country’s northernmost border. A 2012 archaeological survey estimated that the wall (taking into account all the dynasties that had worked on the structure) crosses 15 provinces and extends from Xinjiang, in the northwest, to the border of Korea in the east.

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.