The Great Wall of China is the longest wall in the world, extending approximately 13,171 miles (21,196 kilometers) when all its branches and sections are included. Originally constructed to protect Chinese states from invasions, the wall ranges from walls made of tamped earth to massive stone structures built during the Ming Dynasty. Construction began as early as the 7th century BC and continued until the 16th century AD. Today, the Great Wall is an iconic symbol of China and an architectural feat that represents the country's historical strength and commitment to defense, attracting millions of tourists every year.