Capital. Chang'an, the capital of the Tang dynasty (618-907), was the biggest city in the world at that time, with a population of about two million within its walls and surrounding areas. Chang'an was the heart of the empire, served by a network of roads and canals that connected it to the Silk Road to the west and the Yangzi (Yangtze) River valley to the south. The people of the Tang dynasty knew more about the world than those of the Han dynasty (206 B.C.E.-220 C.E.). Tang people were familiar with regions that had only been known to the Han people by rumor or by occasional and dangerous exploring expeditions. Merchants brought exotic goods from different countries to the markets in Chang'an. Moreover, the city became the meeting place of all kinds of peoples, such...