Built in order to prevent the invasion of the Mongols from the north. The Great Wall of China spans from the Jia-yu Pass of Gansu Province to the Shan-hai Pass of Hebei Province. Extending over 7,300 km and at a height of 8 meters the Great Wall is the longest man-made structure in the world. Great Wall of China is considered one of the Seven Wonders of the World. In 1987, this building was included in the UNESCO World Heritage Site list.