A thousand years of water levels cut into a river shoal

A natural ridge runs under the Yangtze about a kilometre above where the Wu River joins, lying roughly parallel to the channel and close to the south bank. Water has cut it into a western, a central and an eastern section. Through most of the year it lies under the river; only in the winter and spring low-water season does part of it come up. The inscriptions and images are all on the middle section, the broadest and flattest, about 220 metres long. That is the stretch visitors now look at through glass, in water that no longer moves.

The earliest image on the ridge is a pair of stone fish, of which one survives; the earliest text, cut in 764, noted the low water four chi below the fish but has worn away. Among the surviving inscriptions the oldest was cut in 971 and the newest in 1963, about 175 in all, more than half of them from the Song. Since the Tang there has been a saying that when the river falls and the stone fish show, the year will be a good harvest. When the Tang fish had blurred, the prefect Xiao had a fresh pair cut above them in 1685, and the text thickens around both sets.

In 1962 two staff of the Chongqing Museum went to Fuling to survey the inscriptions and noticed their hydrological value. Their survey of historical low water on the upper Yangtze appeared in 1974, and the seventy-two years of levels it recovered were read as a station a thousand years long. The first scheme to protect the site in place, the Crystal Palace, would have had to hold back a head of water forty metres deep and was rejected. In 2001 the academician Ge proposed a shell filled with filtered river water, so the pressure inside matched the pressure outside.

Works began in 2003. The museum opened in 2009 and to the public the year after. Visitors first see a display hall on shore, then take a 91-metre escalator down to a gallery inside the shell, where twenty-three round windows look out at the carvings through still water. It is the first underwater museum in the world where you can see the relics in place without diving. Most of the inscriptions are shown; a few were sealed under water and are not open to view. The whole was listed as a national key cultural relic protection unit in 1988 and put on the tentative World Heritage list in 2008.