Hezekiah's Tunnel

2 Kings 20:20 says Hezekiah "made the pool and the conduit and brought water into the city," and 2 Chronicles 32:30 that he "stopped the upper outlet of the waters of Gihon and brought them straight down to the west side of the City of David." The tunnel, 533 metres long, winds through the bedrock under the City of David from the Gihon Spring in the Kidron valley to the Pool of Siloam, although the two ends are only about 320 metres apart in a straight line. It drops only about 30 centimetres along its whole length. Two teams cut it from opposite ends and met in the middle, as the Siloam Inscription, carved near the Siloam end, describes (see its own entry). It was probably dug around −705, as Hezekiah prepared for Sennacherib's invasion.

Edward Robinson explored it in 1838 and Charles Warren in 1867. Radiocarbon dating of plant matter in its plaster and of stalactites (Frumkin, Shimron and Rosenbaum, Nature, 2003) confirmed a date around −700, though some archaeologists argue for an earlier start. Water still flows through it, and visitors wade it from end to end.