Inhabitants of the Mongolian Plateau have been staunchly nomadic. Cities rarely existed before the Russian hegemony, and at that point they first attached themselves to pre-existing Buddhist monasteries. The exception to this general pattern was the Uighurs, who had an empire in the eighth and early ninth centuries. They built several cities, extended and maintained a flourishing trade network, established sufficient agriculture and developed urban manufacturing. Although historians have pointed out these significant distinctions, few have fully considered the thoroughly revolutionary impact of this Turkish group on steppe culture. One result in the Orkhon Valley was the foundation for Karakorum, the only permanent seat of the imperial Mongols in the thirteenth century. That city occupied the same site and, in the early seventeenth century, served as building material for the major religious centre of Erdene Zuu accompanying the re-introduction of Buddhism. Therefore, the Uighurs affected the physical heartland of their empire for a millennium and the habits of the people to this day.