The Gihon Spring was located outside of the city walls (see red). On top of the water source the Canaanites built a fortress (see blue), allowing access to the water in a time of war. Some of the water went into a pool for storage (as seen immediately to the left of the fortress), while some of the water travelled through a long tunnel (marked by the two aqua lines) which had holes at intervals to water the Kings Garden in the valley below. (City of David Foundation)