Before and after. This schematic view of the Warren’s Shaft and Hezekiah’s tunnel water systems summarizes the author’s conception of how the latter developed. Hezekiah’s tunnel began as a conduit in a natural cave system. Following the conduit, perhaps large enough for a small person to crawl through, teams working from each end dug out a provisional tunnel, as described in the Siloam Inscription (see “Siloam Inscription Memorializes Engineering Achievement”). Then to make a slope for the water to flow from the Gihon Spring to the Siloam Pool, they had to chisel a gradient into the tunnel floor—“straighten down” as the Bible says (2 Chronicles 32:30)—excavating as much as 18 feet of bedrock on the Siloam Pool end. This work left a height difference of only one foot between the two ends—a remarkably exacting feat of engineering. The tinted area marks the excavated material from the downcutting of the channel floor and the addition of the Siloam Pool. This mode of construction fully agrees with the Biblical description.