The famous wall built to protect China from invasions is the Great Wall of China. Construction began in the 7th century BCE, and various dynasties expanded and reinforced the wall over centuries. It served as a defense mechanism against invasions and raids by nomadic tribes from the north, as well as a symbol of the strength and unity of the Chinese states. The wall spans thousands of miles and incorporates various materials and methods, showcasing the remarkable engineering ingenuity of ancient Chinese civilization. It stands today as a UNESCO World Heritage site and a symbol of China's historical resilience.