The Great Wall of China, 1801.
© Science Museum / Science & Society Picture Library
Engraving by J Chapman, showing 'A Sketch of the Chinese Wall, Military Post, and Guard, Watch Tower, and Pagoda'. The wall, which is 1500 miles or 2400 kilometers long, was built to protect China from northern nomads; the earliest sections date from the 3rd century BC, while much of the wall was built during the Ming dynasty (1368–1644). The wall is one of the seven wonders of the modern world, and although much of it has deteriorated, it is still one of the most remarkable structures on the earth, visible from space. Illustration from 'Encyclopaedia Londinensis, or, Universal Dictionary of Arts, Sciences, and Literature' published in London, 1810-1829.