A Mysterious Tunnel Near Jerusalem
Was this how ancient Israelites harvested lime?
Rock-cut entrance to the newly discovered tunnel near Ramat Rahel. Courtesy Israel Antiquities Authority.
Archaeologists excavating near Ramat Rachel in Jerusalem have uncovered an ancient rock-cut tunnel that has so far resisted explanation. The tunnel runs about 165 feet in length, reaches up to 16 feet in height, and measures roughly 10 feet wide. In plain terms, the tunnel is over half the length of a football field, tall enough for people to stand with room to spare, and wide enough for two or three people to walk together. These dimensions speak to considerable investment of labor and planning. However, no inscriptions or small finds have been discovered and the only details to emerge are a few of the tunnel’s features, namely a shaft cut into the ceiling and rock debris on the ground.
The tunnel was accessed via a staircase descending to a hewn (manmade) opening, found filled with layers of soil. Where the tunnel leads, how far it was intended to go, and whether it terminates naturally or was meant to connect to something else are not yet known. That no artifacts have so far been found—no pottery, no coins, no inscriptions—leaves the archaeologists without the basic tools they need to date the tunnel and identify its function.
Two interpretations were initially considered and set aside. The first was that the tunnel was a water installation, like the Siloam Tunnel, designed to reach an underground spring. However, the tunnel walls are unplastered and thus unable to contain or carry water. Plus, there are no known underground water sources in the area. The second possibility—that the tunnel was some kind of agricultural or industrial installation—was judged unlikely given the scale of the construction and the absence of comparable sites nearby.
Archaeologists inspecting the spacious tunnel. Courtesy Israel Antiquities Authority.
The researchers’ current working hypothesis is that the tunnel was intended to reach a chalk layer suitable for quarrying building stones or producing lime. In antiquity, lime was an essential commodity. Limestone was quarried in large quantities and then fired in a kiln at temperatures around 1,650 degrees Fahrenheit (about the same temperature as a glass-blowing furnace, achieved by kiln design, a firebox, and sustained fuel). With carbon dioxide burned off, the rock was reduced to calcium oxide or “quicklime.”
When water is added to quicklime, it becomes “slaked lime,” a white paste with extraordinary versatility. In the ancient Near East, lime was used to plaster cisterns, making them capable of storing rainwater through the dry season. Just as crucially, lime was also used as mortar to bind stone in construction and as whitewash on walls and surfaces. It also has mild antiseptic properties and was spread on agricultural fields to improve soil fertility. Lime was really important, one of the foundational materials of ancient urban and agricultural life. Demand for it in a city like Jerusalem would have been substantial and sustained across many centuries.
Lime production has a direct biblical presence. Deuteronomy 27:2–4 instructs the Israelites to set up large stones, coat them with lime, and inscribe the law on them upon entering the promised land. Amos 2:1 condemns Moab for burning the bones of the king of Edom “into lime.” Isaiah 33:12 uses the imagery of limestone burned to lime as a metaphor for destruction. These references confirm that lime production was a familiar and significant part of the material world the biblical authors inhabited.
If the quarrying hypothesis is correct, the tunnel represents the extraction phase of this process: raw limestone being extracted from the earth before being hauled to the surface and fired in a kiln. Strengthening this interpretation, the ceiling shaft is consistent with a ventilation feature. A tunnel would have required the use of oil lamps, which consume oxygen quickly in an enclosed space, and workers would need airflow to remain in the tunnel for extended periods of time.
The quarrying debris on the floor similarly suggests stone cutting activity took place in the tunnel. The proximity of the site to two known ancient settlements—an Iron Age public building in the nearby Arnona neighborhood and Tel Ramat Rachel, occupied from the Iron Age through the early Islamic period—establishes sustained human activity requiring lime across many centuries.
For readers of the Bible, the discovery of this large tunnel provides occasion to keep up with archaeological discoveries around Jerusalem, and to take a moment to think about lime: a crucial but unglamorous commodity, without which ancient Israel’s cisterns and walls could not have stood.
Lauren K. McCormick is an assistant editor at Biblical Archaeology Review and a specialist in ancient Near Eastern religions, visual culture, and the Bible. She holds degrees in religion from Syracuse University, Duke University, New York University, and Rutgers University, and completed a postdoctoral fellowship on religion and the public conversation at Princeton University.
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