The Great Wall of China is one of the most famous landmarks in the world, and it's a huge construction project that took place over many centuries and involved tens of thousands of workers. The Wall was built as a defensive barrier against the many nomadic tribes who lived on the steppes to the north of China, and it was designed to protect the country from invasion and keep enemies at bay. The wall was originally started in the 7th century BC by the Qin Dynasty, but it was repeatedly damaged and repaired over the years by many Chinese dynasties, the last one being the Ming Dynasty in the 17th century. The Great Wall is today considered a World Heritage Site and a symbol of Chinese culture and history.