Why Did the Founder of the Western Han Dynasty Settle Down in Chang An?
Right after Liu Bang founded the Han Dynasty (206 B.C.-220 A.D.), a large number of his 
followers recommended Luoyang (today's Luoyang city in Central China's Henan Province) as the seat of the capital. However, some others led by the then highest-ranking official Zhang Liang challenged this view, contending that with the surrounding steep mountains, Chang'an was blessed with incredibly favorable topographic conditions that could ensure military success.
In addition, eight rivers encircling Chang'an provided abundant water supply. In the north was the Wa River (Wahe) and the Wei River (Weihe) running from west to east, and in the south were six rivers originating from Mount. Qinling and running from the south to the north. Therefore, with eight rivers encircling Chang'an, the fertile land had great access to irrigation water and consequently an ample yield of farm produce.
The overall nationwide development was also taken into consideration. Since the Emperor Qin Shihuang united various states into a centralized China in 221 B.C., the territory was expanded northward to the grassland and it also stretched to the sea in the east and the south. Therefore, settling down to Chang'an would be helpful in exploring the vast and almost intact eastern region.
The location of the imperial palaces was designed to display the emperors' unchallengea
ble authority.
Topographically speaking, Longshouyuan, the place on which Chang'an was built, runs from the higher southwest to the lower northeast. It's interesting that the archeological record suggests the various kinds of imperial palaces were located in the higher southern region or at least in the middle.
For instance, the city's southwestern corner contained the Weiyang Palace where the emperors met with ministers for official business; in the southeastern corner was the Changle Palace where empresses lived; and in the middle were other palaces for the imperial concubines. On the contrary, commerce centers, handicraft industry workshops, and ordinary people's residences were all arranged in the north.
Such meticulous city planning was not by accident. A place with higher latitude is favorable for ventilation and drainage. In ancient China when such weapons as spears, bows, swords, and so on were widely employed, occupying a relatively higher stronghold was a decisive factor in winning battles.
In addition to concerns over floods and security, an entrenched idea identifying height with power might have played an even more important role. The thinking went that as the nerve center of the whole nation, the front hall of the Weiyang Palace should stand highest to display the unchallengeable imperial authority.
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