In 2012, archaeologists excavating Second Temple-era ruins in the City of David—the oldest part of Jerusalem—found a large underground cistern sealed with the distinctive yellow-brown plaster common in the time of the First Temple. On the basis of its size, they concluded that it was built to serve as a public reservoir. Nadav Shragai explains how the discovery helped answer the question of how ancient Jerusalemites got their water:
For five decades, archaeologists . . . searched in vain for evidence to confirm the . . . testimony woven into a biblical speech of Rab-Shakeh, commander of the Assyrian king Sennacherib’s army. Rab-Shakeh tried to convince Hezekiah, then the king of Judah, and the beleaguered inhabitants of Jerusalem, to surrender: “Come out to me; and eat ye every one of his vine, and every one of his fig-tree, and drink ye every one the waters of his own cistern” (Isaiah 36:16).
For many years, archaeologists searched in vain for the cisterns mentioned by Rab-Shakeh. Many reservoirs were discovered from the Second Temple period, but none from First Temple days. The prevailing assumption, therefore, was that during First Temple times Jerusalem was sustained only by the waters of the Gihon Spring [in the nearby Kidron Valley].
Today, seven years later, Eli Shukron, [the archaeologist who supervised the cistern’s discovery], believes that if he and his colleagues continue searching, they will find other, similar cisterns from that period. The biblical descriptions from the book of Kings of the construction of the Temple by Solomon tell of a “Copper Sea”—a huge water tank made of copper placed in the Temple courtyard—and the ten basins that together had the capacity, in today’s terms, of approximately 120,000 liters (32,000 gallons).
Israel has no plans to dig on the Temple Mount, but it should be noted that the area was mapped and inventoried in the 19th century by Charles Warren, who found 49 cisterns and 42 aqueducts that conveyed water.
Read more on Jerusalem Center for Public Affairs: https://jcpa.org/the-forgotten-discovery-a-secret-water-cistern-from-the-first-temple-era-at-the-foot-of-the-temple-mount/