The Zhaozhou Bridge crosses the Xiao River in the Hebei Province of China and is supposedly the country's oldest standing stone bridge, and maybe the oldest arched stone bridge in the world. It was built during the Sui dynasty about 600 AD by an architect named Li Chun. It is also known as Safe Crossing Bridge (anji qiao), and the Great Stone Bridge (dashi qiao). The bridge is 167 feet long and 30 feet wide, and the middle span is 123 feet across. In the old days horses crossed the bridge, burros crossed the bridge, idlers then as now leaned on the wall and watched the boats, spat in the water and dropped things over the parapet. Cars probably cross the bridge nowadays. Everyone comes and goes. Fish rise to slick boils in the water and then muscle down into the dark. Swallows scribe forgotten geometries in the air around the bridge. The bridge is made out of rock and mortar and is now fourteen hundred years old. The arches are an engineering marvel, but a simple wooden bridge would have done the job in the Sui dynasty, and a concrete bridge would suffice today.
So as it happens 300 years after the bridge was built a monk was visiting a zen teacher called Zhaozhou (who got his name because he lived in the town of Zhaozhou where the bridge was.) The visitor was unimpressed. Not much to see here, said the monk, it's not the bridge I was expecting. Zhaozhou said that's right. The monk then experienced doubt, and a question came into his voice. Some say he asked for more information on the bridge. Zhaozhou may have said you are standing on it. Or he may have said you get from here to there on it.
Zen students have studied this story for over a thousand years.
Here is a photo of the bridge, from a Chinese tourism site.
There is a legend that a magician built the bridge during a single night, and that it was tested by a pair of gods who crossed over it, one with the sun and the moon in a sack, and the other carrying five mountains in a wheelbarrow. The magician saved his handiwork by leaping into the water under the bridge and holding it up. Depictions of the bridge in Chinese art tend to show the magician standing in the water under it, holding it up as the heavenly quality assurance team passed over it.
Though it needed some help holding up that load, the bridge has in fact withstood many floods and earthquakes, the latest earthquake being a magnitude 7.2 tremor in 1966.