Photo Credit: Azriel Yechezkel and Yoav Negev
Reviewing the underground system.

Yes, he may have crucified you know who, but Pontius Pilate, the fifth governor of the Roman province of Judaea, knew how to build an aqueduct. A new study that was published May 30 by Geoarchaeology, conducted by Azriel Yechezkel, Yoav Negev of Israel’s Speleology Club (the folks who explore caves), and Amos Frumkin and Uzi Leibner of Hebrew University, has concluded that Pontius Pilate was behind the construction of the Biar aqueduct (The Shaft Tunnel of the Biar aqueduct of Jerusalem: Architecture, hydrology, and dating). The study was conducted as part of the doctoral dissertation of Azriel Yehezkel from the Institute of Archaeology at Hebrew University

The Biar aqueduct, it turns out, is the most sophisticated of the aqueducts supplying water to Jerusalem during classical periods. It had a total length of five kilometers, including Biar spring, a three-kilometer underground tunnel with dozens of shafts that were used for its construction and maintenance, a dam, an upper aqueduct, and a tunnel traversing a ridge.

Convex gable, a unique roofing method for the Biar aqueduct. / Azriel Yechezkel and Yoav Negev

Yechezkel, Negev, Frumkin, and Leibner conducted a survey of the Biar underground Shaft Tunnel, crawling and mapping all 1200 meters of its accessible parts, and came up with a new understanding of the cutting-edge hydrogeologic and engineering skills used by the Roman engineers and slaves (here’s one for the slaves!) in this project.

According to the study, the last 536 meters of the Biar Shaft Tunnel was constructed with a unique channel made of finely dressed stones (ashlar), divided into segments, designed to withstand different loads:

  1. In a mechanically weak bedrock, a roofed channel with arched gables and barrel vault (specus) was built within a hewn winding tunnel
  2. When dug as an open shallow trench, a channel roofed with complex gables of ashlars with drafted margins was built
  3. To release hydraulic pressure, a channel roofed with alternations of barrel vaults and simple gables set perpendicular to the course of the tunnel was constructed
Underground examination. / Azriel Yechezkel and Yoav Negev

The existence of the Biar aqueduct has been known to scholars for 150 years and to date, various explanations have been offered for the identity of its builders – from the Hasmoneans in the second century BCE through Herod, to the late Roman period after the destruction of the Temple in the second century CE. The new study used Carbon-14 dating of plaster samples that suggested the Biar aqueduct was built in the mid-first century CE and was later renovated in the days of Aelia Capitolina, after the defeat of the Bar Kochva rebellion in the second century CE.

“Due to the fear of a rock collapsing, a wide and high underground tunnel was first hewn,” Yechezkel explained. “After that, a kind of ‘sleeve’ was built inside the tunnel of massive ashlars that were lowered through the shafts.”

This technology was mentioned in the writings of the Roman architect Vitruvius (80–70 BCE –15 CE) in a two thousand-year-old manuscript.

Edging and building a gable complex unique to the Biar aqueduct. / Azriel Yechezkel and Yoav Negev

The Biar aqueduct is part of the system that was used to carry water to Jerusalem. The shortest of the aqueducts that made up the system, Biar carried water from a point south of Bethlehem to Solomon’s Pools. From there, the water was transported through another aqueduct to Jerusalem.

The carbon dating also matches the description by historian Flavius Josephus who wrote that Pilate used the Temple treasury to build an aqueduct. “The people were angry about this, and when Pilate arrived in Jerusalem they surrounded the stage on which he was sitting and shouted against him in a loud voice,” he reported. According to Josephus, Pilate had predicted the protest and ordered his soldiers to hide among the crowd and beat up the protesters (which stands to show you that some things in Jerusalem never change).

“Many Jews were killed under the rain of beatings and many others were trampled at the feet of their comrades in their escape,” Josephus continued. “The people in the crowd were horrified at the fate of those who perished and fell silent.”


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