Jicheng, less commonly called Ji and Yanjing, was an ancient city in northern China, which has become the longest continuously inhabited section of modern Beijing. It has been known by numerous other names over its long history, usually in reference to the changing territories it presided over. Historical mention of Ji dates to the founding of the Zhou dynasty in about 1045 BC. Archaeological finds in southwestern Beijing where Ji was believed to be located date to the Spring and Autumn period (771–476 BC). The city of Ji served as the capital of the ancient states of Ji and Yan until the unification of China by the Qin dynasty in 221 BC. Thereafter, the city was a prefectural capital for Youzhou through the Han dynasty, Three Kingdoms, Western Jin dynasty, Sixteen Kingdoms, Northern Dynasties, and Sui dynasty. With the creation of a Ji Prefecture in present-day Tianjin during the Tang dynasty, the city of Ji became more exclusively referenced as Youzhou or by its subsequent renamings including Yanjing. Youzhou was one of the Sixteen Prefectures ceded to the Khitans during the Five Dynasties. The city then became the southern capital of the Liao dynasty and then the main capital of the Jurchen Jin dynasty. In the 13th century, Kublai Khan built a new capital city for the Yuan dynasty adjacent to Ji to the north. The old city of Ji became a suburb to Khanbaliq/Dadu, whose site was developed under the Ming and Qing dynasties into modern Beijing.