Also known as Anji Qiao (Safe Crossing Bridge) and Da Shi Qiao (Big Stone Bridge), this is often labeled the oldest surviving bridge in China. There are probably older bridges, but this one was constructed between 595 and 605, and unlike China's wooden structures it is largely original in its current form. A mecca for architects and civil engineers as well as historians, it was the first bridge in the world to use a segment of an arc rather than a complete semicircle for its arch, giving a far more shallow curve to the road deck and thus making crossings for carts and horses much easier. This was a major design breakthrough, but it would be 800 years before a similar approach would be tried in Europe, and nearly 1,300 years before Europe tried the spandrel -- piercing the buttresses at either end of the bridge so as to reduce pressure on the foundations and allow floodwaters to pass without sweeping the bridge away.
The parallel stone ribbons that form the main arch are surprisingly flexible and things of beauty in themselves. Until recently the bridge was still in use, but traffic is now diverted, and some of the damaged carvings on the superstructure, including scowling mythical beasts called taotie, have been replaced.
Sadly, the bridge's conversion to a tourist site has brought pedalos (pedal boats) that wallow in the murky, tadpole-filled waters beneath, as well as construction of a hideous parallel concrete pedestrian bridge, mainly to obscure views from the new road bridge and thus increase receipts. But don't let this stop you from viewing China's most significant contribution to architectural method.