The most magnificent waterworks of ancient Jerusalem is Hezekiah's Tunnel. The tunnel is hewn inside the hill in order to protect the access to water from enemies. It channels the water from the Gihon fountainhead to the Shiloah pool, which was within the new walls of the city built by Hezekiah.
King Hezekiah built the tunnel in preparation for the Assyrian siege: "This same Hezekiah also stopped the upper watercourse of Gihon, and brought it straight down to the west side of the city of David." (Chronicles II, 32;30) The external entrance to the Gihon spring was hidden: "... and many people gathered together, and they stopped up all of the fountains" (Chronicles II, 32; 4). Then the waters of the Gihon were channeled through the tunnel to the Shiloah Pool, also built by Hezekiah (Kings II, 20; 20). The pool was located outside the original fortifications of the City of David (Chronicles II, 32; 30), but within the wall that Hezekiah had built. This is the main reason for thereconstruction of the southern part of the wall.
[Archaeology] [Images of selected sites in Jerusalem]