The capital of Vietnam, Hanoi, is a city having over a millennium of history behind it. It has been since the 11th century, whether being the capital of various dynasties of Vietnam in its history. In 1831, it was officially named Hanoi. This city is rich in historical relics and famous places of interest and has been referred to as the "land of millennium cultural relics". Hanoi was originally part of the ancient area of Chinese territory. In 111 BC, Emperor Wu of the Han Dynasty established Jiaozhi County, which Hanoi was affiliated with. The area around Hanoi was already a side settlement during the period of the Southern Song dynasty. The Southern Song has been established Song Ping County in Hanoi with its seat in Changguo County. It was called Songping County during the Sui dynasty and became the seat of Jiaozhi County. This city was founded in 621 AD as Songping County under the Jiaozhou General Administration of the Tang Dynasty of China (later the Annan Protectorate), the political, economic, and cultural center of northern Vietnam at that time; it was also referred to as "Purple City", later relocated to "Luocheng" and finally to "Da Luocheng".