Hezekiah's Tunnel

Hezekiah's Tunnel, or the Siloam Tunnel (Hebrew: נִקְבַּת השילוח, Nikbat HaShiloah) is a tunnel that was dug underneath the City of David in Jerusalem before 701 BC during the reign of Hezekiah of Judah. The tunnel is mentioned in 2 Kings 20:20 in the Bible. The Bible also tells us that King Hezekiah prepared Jerusalem for an impending siege by the Assyrians, by "blocking the source of the waters of the upper Gihon, and leading them straight down on the west to the City of David" (2 Chronicles 32). The tunnel has been securely dated both by the written inscription found on its wall (Siloam Inscription), and by dating organic matter contained in the original plastering. It is one of the few intact, 8th century BC structures in the world that the public can not only visit, but enter and walk through.

The tunnel, leading from the Gihon Spring to the Pool of Siloam, was designed as an aqueduct to provide Jerusalem with water during an impending siege by the Assyrians, led by Sennacherib. The curving tunnel is 533 m long, and by using a 30 cm (0.6‰) gradient altitude difference between each end, conveyed water along its length from the spring to the pool.

According to the Siloam inscription, the tunnel was excavated by two teams, one starting at each end of the tunnel and then meeting in the middle. The inscription is partly unreadable at present, and may originally have conveyed more information than this. It is clear from the tunnel itself that several directional errors were made during its construction. Recent scholarship has discredited the idea that the tunnel may have been formed by substantially widening a pre-existing natural karst.

The difficult feat of making two teams digging from opposite ends meet far underground is now understood to have been accomplished by directing the two teams from above using sounds generated by hammering on the solid karst through which the tunnelers were digging.