Castellum Divisorium, Nimes · Wikimedia Commons

Roman Water-Distribution Tank

Castellum Divisorium

CisternGallia Narbonensis · Nimes, FranceBuilt 45 CE

About

Built around 40-50 CE at the terminus of the fifty-kilometer aqueduct that flowed from a spring near Uzes and crossed the Pont du Gard, this circular stone basin distributed water across Roman Nimes. Water entered through a single channel and left through ten pipes set into the basin wall, each feeding a different quarter of the city. It's one of only two water-distribution tanks of this kind known to survive anywhere from the Roman world, the other at Pompeii. By 117 CE it had quietly done this job for well over half a century.

What happened here

Underground, vaulted, and much larger inside than anything visible above suggests. The walls are lined with waterproof mortar, the corners rounded so nothing can lodge, and the roof carried on rows of piers. Water arrives by aqueduct or off the roofs and is held against the dry months, for a fleet, a bath house, a fort or a whole town. Sediment settles in a trap before the main tank, and the tank is drained and scrubbed on a cycle by men who go down by ladder. Access is through shafts with stairs, and it is cool enough down there that things are stored in them. A town on a dry site lives or dies by its cisterns, and they are among the first things built.