永定河
In the Western Han Dynasty, the river flowed south from Deshengmen through what is now downtown Beijing, including Qianmen and Hongqiao and Longtan Lake, before leaving to the southeast. At that time, the city was southwest of today's city center. In the Liao Dynasty, the river moved southwest to its present course, and the Lugou Bridge was built over it in 1189. When Marco Polo visited the city during the Yuan Dynasty, he crossed the Yongding River on the Lugou Bridge, which became known as the Marco Polo Bridge.