The Gihon Spring is Jerusalem’s major natural source of freshwater. It is located east of the Old Ancient Core (= “City of David”) near the bottom of the Kidron Valley. It is the reason why people first settled on the nearby ridge, rather than on the higher, larger, and more easily defensible western ridge.
“Gihon” means “gushing,” and the name seems to reflect the fact that it occasionally increases its flow. In its natural state it could support about 2,500 people.