2 Chronicles 32:30

This same Hezekiah also stopped the upper watercourse of Gihon, namely, at the approach of Sennacherib's army, and brought it straight down to the west side of the City of David, in a special subterranean canal. And Hezekiah prospered in all his works. Hezekiah's Pool, or reservoir, in the northwest part of Jerusalem still remains, and at least a part of the subterranean channel dug by him has been laid open. 2)