China is known for the Great Wall, an iconic structure that stretches across northern China. The Great Wall was built primarily to protect against invasions by nomadic tribes and to control trade along the Silk Road. Construction began as early as the 7th century BC and continued through various dynasties, with the most famous sections built during the Ming Dynasty (1368-1644). The wall is not a single continuous line but rather a series of walls and fortifications built at different times. Today, it is a UNESCO World Heritage Site and a symbol of China's historical strength and architectural ingenuity.