‘Hezekiah [727- 698 BC] and his officers and champions decided to cut off the water supply from the springs situated outside the city. A great many people were gathered and they stopped all the springs and the brook that flowed through the land [the Solomonic tunnel with its sluices], saying, Why should the kings of Assyria come and find much water?’ (2 Chr.32:2-4). Having thus camouflaged the source of the city’s water supply, Hezekiah ‘constructed the pool and the tunnel to bring water into the city’ (2 Kgs. 2:20); ‘he directed the waters of Gihon down to the west side of the city of David’ (2 Chr.32:30). We know exactly how he did it because of a Hebrew inscription placed by the proud engineer some 10 m inside the tunnel near the pool of Siloam. Had the king ordered the inscription it would have contained his name and been in a much more prominent position! The authenticity of the inscription (now in the Istanbul Museum) is guaranteed by the archaic script and spelling.
A straight line linking the Gihon Spring to the Pool of Siloam is only 323 m. the actual tunnel is in the shape of a huge S, and measures 538 m. the sinuous course suggests that the workmen were following a natural crack in the rock through which water trickled. It alone explains not only how the two teams met, but how they were able to breathe despite the oxygen-eating oil lamps at the work-face.
It is possible to walk through the tunnel starting at the Gihon spring. A flashlight is indispensable. Footwear should be worn. The passage is narrow and low in parts, but perfectly safe, and it is impossible to get lost!
Source: The Holy Land by Jerome Murphy- O’Connor