Warren's Shaft is a vertical shaft next to the Gihon Spring, the main source of water of Bronze and Iron Age Jerusalem, discovered in 1867 by British engineer, archaeologist and military officer Charles Warren. The term is currently used in either a narrower or a wider sense:
After the 19th-century discovery of the vertical natural shaft, it was thought to have been the centrepiece of the city's early water supply system, since it would have enabled the city's occupants to safely reach fresh water in times of siege. This view is still held by many archaeologists, though some believe the shaft was never used in the water system and that it was discovered by chance only during the Iron Age.
In 2005, archaeologists discovered a massively fortified passage connected to a tower above the Gihon Spring. These fortifications appear to have provided secure surface access to the spring from inside the Middle Bronze Age city wall.[1] How these fortifications relate to Warren's Shaft and tunnel remains a matter for discussion.