The Great Wall of China

The Great Wall of China is widely considered one of the greatest engineering feats of all time. Built continuously from the third century BCE to the 17th century CE, this series of walls and natural barriers stretches for around 13,000 miles. (Still, despite a persistent myth, it is not visible from the moon or space, at least not with the naked eye.) The Great Wall was originally the idea of Emperor Qin Shi Huang, the founder of the Qin dynasty and the first emperor of a unified China, who wished to protect the country from barbarian attacks from the north. 

Under his orders, many older, unconnected state walls and fortifications were removed and a number of existing walls were joined into a single system stretching from the eastern Hebei province to Gansu province in the west. The wall itself was 15 to 30 feet high, topped with ramparts of at least 12 feet, with guard towers distributed at regular intervals. Much of the Great Wall that we now see was constructed during the powerful Ming dynasty, starting from around 1474. Today, the most famous and iconic section of the Great Wall of China is located 43 miles northwest of Beijing. This section was rebuilt in the late 1950s and now attracts thousands of tourists every day.