Baopingkou is a key structure of the Dujiangyan Irrigation System, located between Yulei Mountain and Lidui. Built over 2,200 years ago by engineer Li Bing, it was manually carved using fire and water techniques. The 40-meter-long, 17-meter-wide passage adjusts seasonally (19-23 meters wide) to control water flow from the Minjiang River. Its bottle-like shape ("Baopingkou" means "treasured bottle mouth") regulates intake, while Feisha Weir diverts excess water and flushes 75 percent of sediment via centrifugal force. Together, they prevent floods and droughts, sustaining the Chengdu Plain. Join CGTN to immerse yourself in the serenity of this timeless masterpiece.