An inscription incised in the wall of Hezekiah's Tunnel in ancient Hebrew script, approximately six meters from the south end of the tunnel , was discovered in 1880. The inscription was removed from its place in 1890 and transferred to the Istanbul Museum of Antiquities (Turkey). The text describes the last day of work on the tunnel: ... the tunnelling (was finished). And this was the matter of the tunnelling. While [the hewers wielded] / the axe, each man toward his fellow, and while there were still three cubits to be he[wn, there was hear]d a man's voice call/ing to his fellow, for there was a zadah in the rock on the right and [on the lef]t. And on the day / of the tunnelling through, the hewers hacked each man toward his fellow, axe upon axe. And there flowed / the waters from the spring toward the reservoir for two hundre[d and] a / thousand cubits. And a hu[nd]red cubits was the height of the rock above the head(s) of the hewers.

As each team had started from a different end, the work might well have ended with the two groups failing to meet as planned. The existence of a single tunnel is incontrovertible proof that it was meticulously planned and perfectly executed. In this respect, the Hezekiah Tunnel is one of the amazing engineering achievements of Antiquity. The explanation for the engineers' success may be implicit from the text of the inscription itself: 'for there was a zadah (breach) in the rock on the right and on the left'. Perhaps, as some scholars suggested, the reference is to a fissure in the rock, through which water flowed ('the brook that flowed through the midst of the land'; 2 Chronicles 32:4) and which the workmen widened; this would explain the meandering course of the tunnel.

The inscription does no mention the initiator of the project, but the water system and the content of the inscription fit in well with the biblical description of Hezekiah's fears concerning the Assyrian threat and of his preparations (2 Kings 20:20, Isaiah 22:9-11, 2 Chronicles 32:1-4, 30). Interactive Map .