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Ptolemais
About
Seventeen barrel-vaulted cisterns lie beneath a colonnaded plaza at Ptolemais known as the Square of the Cisterns, together holding some 7,000 cubic meters of water for a city with no spring of its own. Roman engineers carried water in from the surrounding hills to fill them, expanding what may have begun as a smaller Hellenistic reservoir. A 2025 excavation even found a human face carved into the plaster on one wall. The system was already old and in continuous use by 117 CE.
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.
Sources
Roman Maps shows the empire frozen at 11 August 117 CE, the day Trajan died — its moment of greatest territorial extent. Explore the full map →