Chang'an's imperial palace covered nearly seven times the Forbidden City's area
The Weiyang Palace in Chang'an sprawled across 4.8 square kilometres, the largest palace ever built. When the Han founder first saw his chancellor's enormous twin palaces, he scolded him for extravagance. The chancellor argued that such magnificence was needed to overawe rivals and prove the dynasty legitimate.
The ground south of the Wei River, in what is now central Xi'an, has been lived on since the Yangshao culture's settlement at Banpo, around 5000 to 4300 BC. The Western Zhou and the Qin both ruled nearby, and the First Emperor's Terracotta Army lies to the east, yet under the Qin, Chang'an itself was only a village. After founding the Han in 202 BC, Liu Bang first settled in Luoyang, as most of his eastern-born advisers urged. A soldier named Lou Jing and the general Zhang Liang persuaded him instead that the Guanzhong basin could feed more people and was far easier to defend.
His chancellor Xiao He rebuilt old Qin palaces as the Changle and then the Weiyang. Thousands of aristocratic clans were forcibly moved to the area, where they could be watched and pointed at the nearby Xiongnu. Walls finished in 191 BC took up to 290,000 labourers on month-long stints plus 20,000 convicts, and their oddly irregular outline was later explained, fancifully, as a copy of the Little Dipper. Emperor Wu later filled two-thirds of the walled area with palaces and built a park lake with three islands of the immortals, a one pond, three hills pattern echoed centuries afterwards at Hangzhou's West Lake and Beijing's Summer Palace. His envoy Zhang Qian's travels west helped make the city the eastern end of the Silk Road.
Rebels sacked it in AD 23, and the Eastern Han moved to Luoyang. Over the next centuries a string of short-lived states made it their capital, and under the Later Qin it became a centre of Chinese Buddhism.
The Sui built a new capital just southeast in 582, renamed Chang'an by the Tang in 618. Around 750 it was called a million-man city, and modern estimates put its walled population at 800,000 to 1,000,000, rivalling Constantinople and Baghdad. In 904 the warlord Zhu Wen forced most residents to Luoyang, and the Ming later walled only a fraction of the old city as Xi'an.
Source: Chang'an
