The Great Wall of China, known as "Chang Cheng" in Mandarin, was built to protect Chinese states and empires from invasions and raids by nomadic tribes and military incursions. Construction began as early as the 7th century BC, with various dynasties contributing to its expansion and fortification over the centuries. The wall stretches over 13,000 miles and incorporates various materials such as earth, wood, bricks, and stones. Beyond its military purpose, the Great Wall symbolizes China's strength and perseverance and has become a cultural icon and a UNESCO World Heritage Site.