Why was the Great Wall built? Did it keep the people of Mongolia out, or to keep the people of China in? How has it come to represent China's past and present as a paradoxical symbol of civilizational glory and political tyranny? For almost 2,000 years, the question of how to handle the nomads of Mongolia was a central question of China's foreign policy. Wall construction, in various places and times, was one of the consistent responses to the "nomad problem." The Great Wall came to symbolize the economic, military, political, and cultural clash between China and Mongolia. It was also a site of diplomacy, markets, and peace-making. Students will explore fundamental questions in frontier history and international relations: do contrasting environments create contrasting cultures? do culture and ideology constrain the responses of policy makers to foreign threats? does crossing a frontier change us? The class covers the 3rd century BCE to the 20th century CE, considering perspectives from both sides of the wall, and the legacy of the Great Wall as an international symbol in the present day.