The famous structure built to protect China from invasions is the Great Wall of China. Construction began in the 7th century BC and continued for centuries. The wall stretches over 13,000 miles and served various purposes, from defense against nomadic tribes to symbolizing the might of the Chinese empire. Its construction utilized various materials, including earth, wood, bricks, and stone, depending on the region. Today, the Great Wall is a UNESCO World Heritage site and a prominent symbol of China's historical strength and architectural ingenuity, attracting millions of tourists each year.