This water tunnel
travels under the city walls and leads outside to the nearby spring.
The water system consisted of a wide shaft, 7 m. deep, with a staircase inside the city, and a tunnel at a 45-degree angle which led down to the water source.
In this way the city would have access to water even during a siege.
Many other major Israelite cities, like Hazor and Megiddo, have
similar highly sophisticated water systems dating to the same period.