shortly after the empire was established, the second son of emperor gaozu of tang, li shimin, king qin of qin, launched the xuanwu gate incident, killed his brothers and brothers, and sat on the throne of the emperor as he wished. in order to show his filial piety to his father, emperor gaozong of tang presided over the construction of the daming palace in the northeast of chang'an city to serve as the li palace for the supreme emperor to escape the summer heat. in 664 ad, the majestic daming palace was completed, covering an area of ​​more than 5,000 acres, equivalent to the size of 500 football fields. starting from emperor taizong of tang, this supreme power center of the empire witnessed the ups and downs of the tang dynasty over the past 222 years. the zhenguan rule and the kaiyuan prosperity were the most commendable glory peaks of the tang dynasty. the anshi rebellion, the ganlu incident, the huangchao uprising, the eunuch tyranny, and the separatist rule of the vassal states left blood-type scars on the body of the empire that could never heal.