The City of David, which was Biblical Jerusalem, is located on a low, narrow spur south of the Temple Mount and today's Old City. A settlement existed here in the Bronze and Iron Ages, of which remains of fortifications and buildings have been found (see Archeological Sites in Israel No.1, pp. 19-23).

The City of David was built on a hill of hard limestone, in which underground water created karstic caves. The Gihon Spring, the only source of water of the city, emerges in the Kidron Valley, east of the City of David. It is mentioned many times in the Bible, e.g., its location in the valley east of the city (II Chronicles 33:14); the anointing of Solomon as King of Israel (I Kings 1:35, 45). It made the founding of the City of David possible, and sustained its existence for thousands of years. The Hebrew name of the spring is derived from the verb meaning "to gush forth," reflecting the flow of the spring, which is not steady, but intermittent, its frequency varying with the seasons of the year and annual precipitation. It is a siphon-type karst spring fed by groundwater that accumulates in a subterranean cave. Each time that space fills to the brim, it empties at once through cracks in the rock and is siphoned to the surface. This natural feature made it necessary to accumulate water in a pool, to be available at times when the spring was not "gushing forth."

The spring emerged in a cave on the eastern slope of the City of David above the Kidron Valley, and from there water flowed into the valley, watering the terraced, agricultural plots on the slope of the City of David. This area is called in the Bible the "King's Garden" (II Kings 25:4; Jeremiah 52:7; Nehemiah 3:15). Today, the bed of the Kidron Valley is filled with 15 m. of erosion and debris, which have accumulated over the millennia. During the Second Temple period, a vault was built over the spring, to which one could descend via a long staircase. Water flowed from the spring along Hezekiah's Tunnel to the Siloam Pool, (John 9:7) which is located in the low, southern part of the Tyropoeon Valley, west of the City of David.

Three waterworks, fed by the Gihon spring, were carved into the rock beneath the City of David in antiquity and they are the most complex and advanced of any known from Biblical cities. The systems were planned in different periods, served varied purposes and functioned in distinct ways. All three water systems were in operation simultaneously in the First Temple period, and each contributed to the efficiency of the city's water supply. They also attest to the efforts of the kings of ancient Jerusalem to guarantee the water supply in time of siege.

The "Warren's Shaft" System

In times of war and siege, the City of David's water supply was vulnerable, since the Gihon spring in the Kidron Valley was outside the city walls. The "Warren's Shaft" System is the earliest subterranean water system and, filled with accumulated debris, it was discovered by C. Warren in 1867 and named after him. Investigation and documentation were conducted by H. Vincent (1909-1911). In the early 1980s, the Warren's Shaft System was cleared and reinvestigated by Y. Shilo and, since 1995, new research included excavation of the eastern extremity of the shaft.

The entrance to the Warren's Shaft System is located in the middle of the eastern slope of the City of David, within the ancient city's walls. It consisted of a subterranean, rock-cut tunnel with a shaft at its end. At the entrance, the tunnel slopes steeply downward in a stepped passage. This portion is covered by a well-constructed vault from the Second Temple period, which prevented soil and rocks from falling into the system. Farther down, the tunnel becomes less steep. At first, it extends in a northeasterly direction, then angles sharply to the southeast. The total length of the tunnel is 41 m. and it descends 13 m.; its width is 2.5-3.0 m. and its height varies from 1.5 m. at the entrance to a maximum of 5 m. At its easternmost end is a narrow, irregularly shaped vertical shaft some 2 m. wide and 12.5 m. deep, which leads to the waters of the Gihon Spring; going down the tunnel to the shaft, water could be drawn with a container fastened to a rope. Thus, in time of siege it was possible to safely draw water from the spring without venturing outside the walls. The narrow vertical shaft at the end of the system was impenetrable from the outside.

Most scholars were in agreement that the Warren's Shaft System was man-made and the product of a tremendous effort. However, a hydrological study conducted at the beginning of the 1980s, established that the shaft and most of the tunnel were natural karstic fissures in the rock. The planners of the system had taken advantage of these, combining and adapting them in cutting a complete system that made subterranean passage from the city to the spring possible.

On discovery of the Warren's Shaft System it was proposed to identify it with the tsinnor (Hebrew, pipe or shaft) mentioned in the Bible in the description of David's conquest of the city (II Samuel 5:8): And David said on that day, whosoever gets up to the tsinnor, and smites the Jebusites The meaning of tsinnor is problematic and a parallel description of the city's conquest by David (I Chronicles 11:4-7) fails to mention it. For this reason, and in light of comparative archeological research, the identification of the Biblical tsinnor with the Warren's Shaft System was not accepted by most modern archeologists. Such an identification would have meant dating the tsinnor to the period of Canaanite and Jebusite rule in the city (i.e., prior to David's conquest in the 10th century BCE), for which there was no archeological evidence. It should also be noted that other Biblical cities (Megiddo, Hatzor) had water systems combining similar elements, and these are dated to the period of the Divided Monarchy (9th century BCE).

This was the accepted theory about the Warren's Shaft System until renewed research in the 1990s. Next to the Gihon Spring, remains of fortifications and of a waterwork from earlier days of Jerusalem were unexpectedly uncovered. Exposed were two massive towers of enormous stones that protruded eastward from the line of the city wall. Between them was a very deep rock-cut pool. The towers protected the spring and the pool, denying access to them while guaranteeing the water supply in time of siege. The excavators dated this fortification system to the beginning of the 2nd millennium BCE (Canaanite period).

The short section of the tunnel from the low eastern end of the Warren's Shaft was cleared during the new excavations and found to lead to the surface on the eastern slope of the City of David, opposite the pool and towers just described. This new research supports the old view that the Warren's Shaft system was entirely man-made, by two teams of workmen beginning work on opposite sides.

According to this new view, the Warren's Shaft System consists of two chronologically distinct phases of rock cutting. In the first phase, on construction of the towers and the pool near the spring (at the beginning of the 2nd millennium BCE), the upper part of the system was cut into the soft chalk. This low tunnel followed a curving course with a gradual slope to its outlet on the surface, opposite the rock-cut pool protected by the towers. In the second phase (8th century BCE, under the United Kingdom), the tunnel was deepened and cut into harder rock. Work was stopped when the tunnel encountered the top of the vertical shaft, through which water could be drawn from the Gihon Spring.

This new research, though leaving several important problems unresolved, nevertheless enables us once more to consider its possible connection to the Biblical tsinnor.

The Siloam Channel

The Siloam Channel, cut at the beginning of the 2nd millennium BCE, emerges from the Gihon Spring and extends approximately 400 m. southward along the low, eastern slope of the City of David, around the city's southern end and empties into a reservoir in the Tyropoeon Valley. The channel's northern part is 2.75 m. deep and is covered by large stones; the southern part is open, but becomes a rock-cut tunnel towards the end. Openings along the channel allowed water to flow out and irrigate the terraces on the eastern slope of the City of David.

Some identify the Siloam Channel with the waters of Shiloah that go softly (Isaiah 8:5). It was blocked after the cutting of Hezekiah's Tunnel. The biblical passage referring to this is probably II Chronicles 32:4: So a great many people were gathered together, who stopped up all the springs, and also the wadi that ran through the midst of the land, saying, Why should the kings of Ashur (Assyria) come and find much water?

Hezekiah's Tunnel

Hezekiah's tunnel is the latest and most impressive of the water systems built in the City of David. Although its existence was known hundreds of years ago, its systematic investigation was undertaken only in the last century. Clearance of the tunnel, thorough study and mapping were carried out by H. Vincent between 1909 and 1911. The Siloam Inscription, discovered in the tunnel at the end of the 19th century, was removed and is today in the Archeological Museum of Istanbul.

The tunnel was cut into the rock beneath the City of David, in a 533 m.-long, "S"-shaped course. In a straight line, the distance from the Gihon Spring to the Siloam Pool is only 325 m. The average width of the tunnel is about 60 cm.; it is about 2 m. high along most of its course, but reaches 3 - 4 m. in some sections at the beginning and the end. The Tunnel was finely carved out, with chisel marks visible. The downward slope from beginning to end is very gentle, approximately 2 m. altogether, with an average decline of 0.4%.

The tunnel was cut during the reign of King Hezekiah of Judah (end of 8th century BCE) and described in detail in a six-line inscription, in paleo-Hebrew script, cut into the rock near the exit:

"breakthrough and this was the account of the breakthrough. While the laborers were still working with their picks, each toward the other, and while there were still three cubits to be broken through, the voice of each was heard calling to the other, because there was a zdh [crack?] in the rock to the south and to the north. And at the moment of the breakthrough, the laborers struck each toward the other, pick against pick. Then the water flowed from the spring to the pool for 1,200 cubits. And the height of the rock above the heads of the laborers was 100 cubits."

The project is mentioned in the Bible (II Kings 20:20): "...and how he made a pool, and a conduit, and brought water into the city" and again in II Chronicles 32:30: "This same Hezekiah also stopped the upper watercourse of Gihon, and brought it straight down to the west side of the city of David."

In view of the threat of an Assyrian invasion of Judah, work on the fortifications and the cutting of the tunnel had to be carried out in great haste. Included was a fortified wall surrounding the western hill (Mt. Zion and the southern part of today's Old City), thus including the Siloam Pool in the Tyropoean Valley, within the city walls.

The curving course of Hezekiah's Tunnel, and the description of how it was cut by two teams of workers, raises questions about engineering and planning capabilities enabling the two teams to meet; not a simple matter considering that work was carried out in the depths of the earth, with minimal lighting by oil lamps, and with little oxygen. There must have been a reason for the long, curving route, requiring so much more effort than a straight one. Several explanations have been proposed over the years. According to one, the workmen followed curving rock formations; another, erroneous one, was that the curve was intended to bypass the (mistakenly identified) Tombs of the House of David; the most probable explanation is that the workmen followed a crack in the rock through which some water flowed from the Gihon to the Tyropoean Valley. The Siloam Inscription mentions that "there was a zdh in the rock", which could be interpreted as a crack (geological, or the result of karstic activity, or both), in which some water flowed, and which they enlarged into a tunnel. The entrance to the spring in the Kidron Valley was then skillfully disguised.

Since removal of the debris that blocked Warren's Shaft, it has been open to visitors. Hezekiah's Tunnel may also be traversed, walking through the water that flows in it to the Pool of Siloam.

The Warren's Shaft System was cleared and examined by the Y. Shilo expedition to the City of David (1978-1985) on behalf of the Hebrew University of Jerusalem, the Israel Exploration Society and the Jerusalem Foundation. Under its auspices, a hydrological survey of the water system was carried out by D. Gil. New excavations have been conducted since 1995 by R. Reich and E. Shukron on behalf of the Israel Antiquities Authority.