SILOAM sī lō’ əm (Σιλωάμ, G4978, sending). A pool and tower in Biblical Jerusalem. The term is also currently applied to the water tunnel that empties into the pool.

As a defense against the attacks by Assyria, which culminated in Sennacherib’s campaign of 701 b.c. (cf. 2 Chron 32:4), Hezekiah of Judah constructed the Siloam water tunnel from the Gihon spring, southwestward through the rocky core of Mt. Zion, and out into the central Tyropoeon Valley of Jerusalem, q.v., II, C (v. 30). The tunnel is square cut, averaging two ft. wide and six ft. high. It follows an S-shaped course, so that the direct distance of 1090 ft. involves 1750 ft. of actual tunneling. This may reflect attempts to avoid harder rock formations or deeply cut structures at higher levels, as tombs; certain of the turns were produced as the crews, working inward from both ends simultaneously, sought to contact each other. As it turned out, considerable additional construction became necessary in the S portion, namely, a lowering of the tunnel floor in order to allow a gravity flow of the water. An inscr. just inside the SW portal was discovered in 1880, which has now been cut out from the rock and removed to the Istanbul Museum. Literally tr. from the archaic Heb. (Phoen.) letters it reads: “The boring through [is completed]. And this is the story of the boring through: while yet [they plied] the drill, each toward his fellow, and while yet there were three cubits to be bored through; there was heard the voice of one calling unto another, for there was a crevice in the rock on the right hand. On the day of the boring through the stonecutters struck, each to meet his fellow, drill upon drill; and the water flowed from the source to the pool for a thousand and two hundred cubits, and a hundred cubits was the height of the rock above the head of the stone cutters” (E. Kautzsch, Gesenius’ Hebrew Grammar, frontispiece: photograph, tracing, and transcription into square character).

While the aforementioned pool may have remained outside the city walls as a covered cistern, with additional, concealed access tunnels and overflow channels (K. Kenyon, Jerusalem, 70-77), the water seems actually to have come “into the city” (2 Kings 20:20), prob. through an as yet unrecovered extension of the SW fortifications of Zion (cf. 2 Chron 32:5, “another wall”). Isaiah appears to speak of Hezekiah’s “reservoir between the two walls for the water of the old pool” (Isa 22:11). This latter pool may refer to an original, upper pool (7:3), near the Gihon spring. A lower pool (22:9), modern Birket el-Hamra (?), at the S tip of the pre-Hezekian city is known to have received water from it by a surface conduit called הַשֶּׁ֨לַח׃֙, LXX, τοῦ Σ(ε, G1567) ιλωάμ, the sending (one), sender (8:6; cf. Jerusalem, II, B). The course of its upper 200 ft., with a minimal drop along the E side of Mt. Zion—“waters of Shiloah (q.v.) that go softly”—is still traceable. By postexilic times, at least, the lower pool itself came to be called הַשֶּׁ֨לַח׃֙, Shelah (KJV Siloah), with the same meaning (Neh 3:15), since it seems to have continued in use for overflow from Hezekiah’s newer pool.

By Christian times the name Siloam had, understandably, become transferred to the newer pool; for Josephus refers to the πηγή, G4380, spring, fountain, by which he intended the water at the outlet of Hezekiah’s tunnel (War V. 4. 1, 2). The Tower of Siloam, which collapsed at the cost of eighteen lives (Luke 13:4), must have stood on the slope of Mt. Zion to its E. The NT thus designates this pool, to which Jesus sent the man who had been born blind, as the Pool of Siloam and appropriately interprets it to signify “sent” (John 9:7). Traces remain of a Herodian reservoir and bath structure, c. seventy ft. square, with steps on the W side. Here the man would have washed, and he miraculously received his sight (vv. 8, 10).

A commemorative Byzantine church was constructed just NW of the reservoir in c. a.d. 440 by the Empress Eudocia, together with elaborate porticoes about the pool. Only fragments remain visible, and the pool itself now rests eighteen ft. below the surrounding ground level. The surviving pool carries the title Birket Silwan, may be reached by a steep flight of stone steps, and measures 16X50 ft. A small mosque stands over the ruins of the church, and the name Silwan has become attached to the Arab village across the Kidron Valley to the E.

Bibliography G. A. Smith, Jerusalem (1907), I: 91-98; H. Vincent and F.-M. Abel, Jérusalem Nouvelle, IV (1926), 860-864; J. Simons, Jerusalem in the OT (1952), 175-194; H. Vincent, Jérusalem de l’At, I (1954), 264-284, 289-297; IDB, IV: 352-355; K. Kenyon, Jerusalem, Excavating 3000 Years of History (1967), 69-77, 96-99.