The Western Han dynasty (206BC-8AD) moved the capital to within ten kilometres of Xi'an, to a city called Chang'an. It became the economic and cultural center of China. Many magnificent buildings were constructed, including the Shangle, Weiyang, and Chengzhang Palaces, as well as the imperial garden Shangliyuan. The ancient trading route, the Silk Road, was established during that time, and silk, paper, tea, iron casting and irrigation and other inventions were exported to the West. At the easternmost point of the route, Xi'an was China's first city open to the world. It was during this period that trade also began with West Asia and the Roman Empire. Just as in present-day China, a special street was set aside to accommodate foreign visitors and a protocol department supervised their undertakings.

In the 5th century, the Sui Dynasty rebuilt Chang'an on the plain where modern Xi'an now stands. After the Eastern Han dynasty (8-220 AD) transferred the imperial capital to Luoyang, it didn't return to Xi'an until China was once more reunified under the Sui dynasty (589-618). Once more the grandiose schemes of a despotic, conquering Emperor were curtailed by a dynasty more amenable to the people.

During the golden age of the Tang dynasty (618-907), when China led the world in culture, technology and wealth, Chang'an became a focus for new ideas. A vast and splendid city of eighty square km, only twenty less than today's industrialized city, it contained a two million strong population. So beautiful were its buildings and so orderly was its design that the Japanese used Chang'an as the model for the already existant, smaller cities of Kyoto and Nara. By the 7th century Chang'an had become the largest and most cosmopolitan city in the world.

Skipping a few centuries and many name changes, Xi'an during the Ming dynasty was refurbished and returned to prominence as a center of politics and trade. The Ming emperors rebuilt the walls, incorporating one corner left over from the Yuan dynasty into their design.  While the architecture of the Ming is steadfastly angular, the curved rampart of Hun design added grace to the design. The walls are flat and straight, making them tempting for a 15km jog. Altogether, the town of Xi'an during the Ming and Qing Dynasties was not much larger than the Tang Imperial Palace. Growth, if not glory, began again in 1949; new industries and universities were built, and the population has quadrupled to two million. The cultural and historical significance of the area, as well as the abundant relics and sites, helps Xi'an to enjoy the laudatory title of being a "natural history museum".