"Warren's Shaft" or: Digging Through the Labyrinth of Biblical Archeology
Until recently it was thought that the Jebusite city conquered by David was a fortified yet small city with few impressive architectural features. The most intriguing feature of the pre-Israelite city as it was imagined by biblical archeologists is the so-called "Warren's Shaft," named after the British engineer Sir Charles Warren who (in 1867) first discovered a crevice in the rock above the Gihon Spring that was later thought to have been the main water supply of the Jebusites from within the city. While it is now assumed that "a natural sinkhole along a joint in the limestone" (Armstrong p. 6) facilitated the creation of this tunnel, its function continued to be assumed until a few years ago to allow residents of the walled city to draw water from a pool near the Gihon Spring without exposing themselves to danger. Biblical archeologists identified this "tunnel" with a feature referred to in 2. Samuel 5:8, the most ancient literary account of David's conquest of Jerusalem (but not written down until centuries after the event it commemorates), where a pipe or "gutter" is mentioned through which David's general Joab was able to enter the city and take it by force. This detail of the story is later no longer understood, which is the reason why, a thousand years after David, Josephus describes the conquest in his The Antiquities of the Jews in terms more attuned to how the city looked in his own time.
Recent excavations in the City of David, however, have begun to produce a completely different picture of the city preceding its Israelite conquest. It is now clear that the city was much larger than had been hitherto assumed and the water system fed by the Gihon Spring was much more elaborate, featuring a wall and massive tower dated to the 18th century BCE and structures that allowed comforable access to the water system from within the city.
What makes this shift in our knowledge about the ancient city difficult to accept for some and exciting for others is its relation to what we know from the main literary source available to us, i.e., the Bible. The school of "Biblical archeology" (beginning with Protestants like Charles Warren but more recently also joined by Catholics and Jews) has been trying to use archeology to verify biblical accounts and thus restore historical trust of the Bible's accounts, a trust shaken by modern biblical studies and its inherently critical historical attitude.
For a brief overview of the recent findings see:
http://www.mfa.gov.il/MFA/Israel+beyond+politics/Archeology-+News+from+the+Field+10-Aug-2005.htm
For further reading see the following literature on the excavations of the ancient water system of the Jebusite city
a) Literature representing the scholarly assumptions about the size, location, and water system of the Jebusite city that were standard until recently and are still widely reiterated (esp. on the internet):
Avigad, N.: Discovering Jerusalem, Nashville (1993) 13-60.
Shiloh, Y.: “The Rediscovery of the Ancient Water System Known as ‘Warren's Shaft’”, in Ancient Jerusalem Revealed, Jerusalem (1994) 46-54.
Cahill, J.M. and Tarler, D.: “Excavations Directed by Yigal Shiloh at the city of David, 1978-1985”, in Ancient Jerusalem Revealed, ed. Geva, H., Israel Exploration Society, Jerusalem (1994) 31-45.
b) Works by Reich, R. and Shukron, E. describing the recent excavations in the City of David:
New Excavations in the City of David. Pp. 3-8 in New Studies on Jerusalem, Proceedings of the Third Conference, eds. E. Baruch and A. Faust. Ramat Gan: Bar-Ilan University (Hebrew).
1998
Jerusalem, Spring of Gihon. Hadashot Arkheologiyot (Archaeological News) 108:136-37 (Hebrew).
1998
The Tunnel System and Excavations Adjacent to the Gihon Spring. Pp. 5-134 in New Studies on Jerusalem, Proceedings of the Fourth Conference, ed. E. Baruch. Ramat Gan: Bar Ilan University (Hebrew).
1999“Warren’s Shaft Theory of David’s Conquest Shattered”, in BAR 25.1 (1999) 22-33.
Light at the End of the Tunnel. Biblical Archaeology Review 25.1:22-33 and 72.
2000
The System of Rock-Cut Tunnels Near Gihon in Jerusalem Reconsidered. Revue Biblique 107:5-17.
2002
Reconsidering the Karstic Theory as an Explanation to the Cutting of Hezekiah's Tunnel in Jerusalem. Bulletin of the American School of Oriental Research 325:75-80.