Hezekiah's Tunnel

Never Lost, Only Measured

Most of the objects in this section had to be found. This one was never missing. The tunnel runs from the Gihon Spring, in the Kidron Valley outside the ancient wall, to the Pool of Siloam inside it, and people have waded through it for as long as there have been people in Jerusalem. What the nineteenth century added was measurement. E. Robinson traversed it in 1838 and published a description; C. Warren surveyed it for the Palestine Exploration Fund in 1867, during the same campaign that produced the shaft named after him. The tunnel is about 533 metres long. The difference in height between its two ends is roughly 30 centimetres — a gradient of about 0.06 per cent, which is to say almost nothing, and enough.

The detail that has fascinated engineers ever since is that it was cut from both ends at the same time. The two teams met in the middle, and the joint is visible: the chisel marks change direction, and there is a short section of false starts where the crews were hunting for each other through the rock. In 1880 a boy exploring the tunnel noticed six lines of paleo-Hebrew cut into a smoothed panel a few metres from the Siloam end. That is the Siloam Inscription, which this app treats in its own article, and it is the tunnellers' own account of the moment the two crews broke through.

Water Inside the Wall

2 Kings 20:20 credits Hezekiah with making the pool and the conduit and bringing water into the city. 2 Chronicles 32:30 is more specific: he stopped the upper spring of the waters of Gihon and brought them straight down on the west side of David's city. And 2 Chronicles 32:2-4 gives the reason — Sennacherib was coming, and the springs outside the walls were stopped so that the Assyrians would not find abundant water. Isaiah, writing at the time and not approving, describes a reservoir made between the two walls for the water of the old pool, and complains that the men who built it did not look to the one who purposed it long ago.

The tunnel matches that description at every point a description can be matched. It moves the water supply from outside the defensive line to inside it. Its course is an odd, wandering S rather than a straight line, which is what you get when speed matters more than elegance. It was cut from two directions at once, which is what you do when you are in a hurry. It is not a small work: it is among the largest engineering works surviving from the Judahite monarchy, and it still functions.

One consequence is worth naming for a reader who knows the Gospels better than the Iron Age. The pool at the tunnel's outlet is the Pool of Siloam, and the pool Jesus sends a blind man to wash in, in John 9:7, is fed by this conduit. The Second Temple pool excavated in 2004 is not the same basin Hezekiah's men filled — seven centuries lie between them — but the water arriving in it came down this tunnel.

How the Date Was Settled, and What Is Still Argued

The Hezekiah attribution was challenged directly. J. Rogerson and P. Davies argued in 1996 that the tunnel and its inscription were Hasmonean, some five centuries later than the usual date, chiefly on the letter forms. That proposal was answered by physical evidence rather than by argument. A. Frumkin, A. Shimron and J. Rosenbaum dated organic material sealed inside the tunnel's original plaster by radiocarbon, and the speleothems that grew on the plaster afterwards by uranium-thorium, and published the result in Nature in 2003: an Iron Age II date, around 700 BC. It was the first securely identified structure named in the Hebrew Bible to be dated radiometrically, and it is why the date can be stated at full strength here.

Two arguments remain genuinely open. The first is about a few decades. R. Reich and E. Shukron, from their long excavation at the Gihon Spring, have argued for a date somewhat earlier than Hezekiah's reign — the end of the ninth century or the first part of the eighth. That is a real disagreement between specialists, and it is a disagreement about which Judahite king, not about whether the tunnel is Iron Age. The second is about method: A. Sneh, R. Weinberger and E. Shalev argued in the Bulletin of the American Schools of Oriental Research in 2010 that the tunnellers largely followed and widened an existing natural karstic fissure, which would make the achievement a different kind of achievement. A. Shimron and A. Frumkin replied in the same journal the following year, defending the tunnel as an artificial cut. That exchange is unresolved in the sense that both papers are on the shelf; most subsequent work has followed the artificial reading.

The limit worth stating plainly is smaller than the tunnel. Nothing in it names a king. The inscription at the Siloam end describes the breakthrough and does not say who commissioned the work. The link to Hezekiah rests on the radiometric date landing in his reign, on the tunnel doing exactly what 2 Chronicles 32 says he did, and on the absence of any other candidate — a strong convergence, and still a convergence rather than a signature.

Scripture references

• 2 Kings 20:20 — Hezekiah made the pool and the conduit and brought water into the city
• 2 Chronicles 32:30 — The upper spring of Gihon stopped and brought down on the west side
• 2 Chronicles 32:2-4 — The reason: Sennacherib coming, and the springs outside the city stopped
• Isaiah 22:11 — "You also made a reservoir between the two walls for the water of the old pool"
• John 9:6-7 — The pool at the tunnel's outlet, seven centuries later

Sources

• Holding institutionPalestine Exploration Fund — The Palestine Exploration Fund, founded 1865 · The body that sponsored C. Warren's Jerusalem excavations of 1867-1870, which produced the first careful survey of the tunnel and of the shaft named after himSupports: The nineteenth-century survey history
• ScholarshipA. Frumkin, A. Shimron and J. Rosenbaum, "Radiometric dating of the Siloam Tunnel, Jerusalem" — Amos Frumkin (Hebrew University), Aryeh Shimron, Jeff Rosenbaum · Nature 425 (September 2003), 169-171, doi:10.1038/nature01875. Radiocarbon on plant material in the original plaster and uranium-thorium on the overlying speleothems. Behind a publisher paywall; the bibliographic record was confirmed through Crossref · paywalledSupports: The c. 700 BC date, and the refutation of a Hasmonean dating
• ScholarshipA. Sneh, R. Weinberger and E. Shalev, "The Why, How, and When of the Siloam Tunnel Reevaluated", with the reply by A. Shimron and A. Frumkin — Bulletin of the American Schools of Oriental Research · BASOR 359 (2010), 57-65, and the reply at BASOR 364 (2011), 53-60. The exchange over whether the tunnellers followed a natural karstic fissure · paywalledSupports: The live methodological dispute in the third section
• ScholarshipJ. Rogerson and P. Davies, "Was the Siloam Tunnel Built by Hezekiah?", and R. Reich and E. Shukron, "The Date of the Siloam Tunnel Reconsidered" — John Rogerson and Philip R. Davies; Ronny Reich and Eli Shukron · The Biblical Archaeologist 59:3 (1996), 138-149, and Tel Aviv 38:2 (2011), 147-157. The Hasmonean proposal that the radiocarbon answered, and the excavators’ case for a date somewhat earlier than Hezekiah. Both records confirmed through Crossref · paywalledSupports: Both dating challenges named in the third section
• EncyclopediaWikipedia: Siloam tunnel

Further reading

• Wikipedia: Siloam tunnel
• Palestine Exploration Fund

Reflect

Two crews cut toward each other for months through solid rock, unable to see or hear the far end, trusting they would meet. Where are you working toward someone you cannot yet hear?