Zhaozhou Bridge, also called Anji Bridge, is the Chinese stone bridge built around 605 that is recognized as the world’s oldest surviving open-spandrel segmental arch bridge.
The bridge crosses the Xiao River near Zhao County in Hebei Province. It was traditionally attributed to the engineer Li Chun and was constructed during the Sui dynasty, making it an exceptionally early surviving example of advanced stone-arch engineering.
Its main arch is segmental rather than semicircular, meaning it forms a relatively shallow curve. Smaller arches within the spandrels reduce the amount of stone and help lighten the structure while allowing floodwater to pass through.
Zhaozhou Bridge has survived repeated floods, earthquakes and centuries of repairs. It is often confused with Lugou Bridge, also known as Marco Polo Bridge, which is a later stone bridge near Beijing.