Great Wall of China
This is the Great Wall of China. The structure is over 2,300 years old and stretches 13,170 miles (21,196.18 km). It is the longest wall on Earth. Imperial China built the structure to protect the country from nomadic groups and use it as border control. The Chinese initially constructed separate walls but began joining them during the Qin Shi Huang (220–206 BCE). The most significant additions to the wall were built during the Ming Dynasty (1368-1644). According to Travel and Leisure Magazine, the structure received around 10 million visitors every year as of 2017.