A recently published study has revealed that ancient Jerusalem’s water infrastructure included a tunnel longer than any known from the Roman Empire. The finding appears in the June 2025 issue of the journal Groundwater and was authored by David Deming of the University of Oklahoma.
In the peer-reviewed article, titled The Aqueducts and Water Supply of Ancient Jerusalem, Deming examines Jerusalem’s extensive water system developed over millennia to sustain the city through droughts, sieges, and religious festivals. The most surprising revelation is that the Wadi el Biyar aqueduct, which fed water into Solomon’s Pools near Bethlehem, includes a 2.8-kilometer tunnel—making it longer than any tunnel in the aqueduct systems of ancient Rome.
“The Wadi el Biyar tunnel was cut into a rock layer that has the properties of an aquifer,” Deming wrote. “It directly supplemented the water drawn from the spring.” To construct the tunnel, workers dug vertical shafts approximately every 35 meters and excavated horizontally in both directions. These shafts served not only to remove debris but also provided ventilation and access for future maintenance.
According to Deming, the longest known aqueduct tunnel supplying ancient Rome was the Anio Novus, at 2.25 kilometers. “Remarkably, [Wadi el Biyar] is longer than any tunnel in the water supply system of ancient Rome,” he noted, referencing work by Mazar and others.
The article, published by Groundwater on behalf of the National Ground Water Association, underscores the sophistication of Jerusalem’s ancient engineers. The aqueducts—including the Wadi el Biyar, the Arrub, the Upper (High Level), and Lower (Low Level) systems—brought water from the Hebron Hills into the city, with tunnels, siphons, and settling pools playing critical roles.
Deming suggests that the construction of the Wadi el Biyar tunnel may date to the reign of Herod the Great (c. 72–4 BCE), based on architectural style and nearby historical references by Josephus.
The study concludes that “the very existence of Jerusalem was made possible by a reliable water supply,” and the scale and endurance of its hydraulic engineering rival those of Rome.
The preparation of this article relied on a news-analysis system.