Ancient city in northern China
Ji or Jicheng was an ancient city in northern China, which has become the longest continuously inhabited section of modern Beijing. 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 Jizhou (蓟州) during the Tang dynasty in what is now Tianjin Municipality, the city of Ji took on the name Youzhou. 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 main capital of the Jin dynasty (1115–1234). 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 Dadu. In the Ming dynasty, the old and new cities were merged by Beijing's Ming-era city wall.