Although the translation of the Hebrew text at 2 Samuel 5:8 presents certain problems, the usual rendering indicates the presence of a “water tunnel,” referred to by David when promoting the attack on the city. In 1867 C.E., Charles Warren discovered a water channel running back from the cave in which the spring of Gihon rises and, after a distance of some 20 m (66 ft), ending in a pool or reservoir. A vertical shaft in the rock above this pool extended upward 11 m (36 ft), and at the top of the shaft there was a place where persons could stand and let down containers by rope to draw water from the pool below. A sloping passageway led back nearly 39 m (128 ft) from the shaft up into the interior of the city. By this means it is believed that the Jebusites maintained access to their water source even when unable to venture outside the city walls because of enemy attack. Although the spring of Gihon is not directly mentioned in the account, it is suggested that Joab and his men daringly gained entrance to the city through this water tunnel.

When Assyrian attack became imminent in Hezekiah’s reign (732 B.C.E.), King Hezekiah took measures to ensure that Jerusalem’s supply of water would not fall into the hands of the enemy. (2Ch 32:2-4) However, possibly with reference to another time, the record at 2 Chronicles 32:30 shows that he shut off the flow of the Gihon through its previous channel and diverted the waters to the western side of “the City of David,” well within Jerusalem’s fortifications. Evidence of the manner in which this was accomplished came to light in 1880 C.E. when an inscription was found carved in the wall of a water tunnel terminating in what is presently known as the Pool of Siloam on the W side of the old “City of David.” The inscription, in early Hebrew script regarded as dating from the eighth century B.C.E., described the excavation of the tunnel through solid rock by the two teams of men working toward each other from opposite ends. When the tunnel was completely cleared in 1910, it was found to measure some 533 m (1,749 ft), with an average height of 1.8 m (6 ft) and at times narrowing to a width of only 0.5 m (20 in.). It seems evident that this remarkable engineering feat is the result of Hezekiah’s measures to protect and maintain Jerusalem’s water supply originating in the Gihon.