Jerusalem, Israel, is one of the oldest continuously inhabited cities in the world, and a holy place for the Jewish, Christian and Muslim religions. The oldest part of Jerusalem, known as the City of David, owes its development to an important geologic feature: a freshwater source called the Gihon Spring
 
Originating at the base of the hill on which the City of David was constructed, the Gihon Spring’s waters emerge from a cave on the city’s eastern slope before flowing into the adjacent Kidron Valley.  
 
Professor Rehav Rubin, who teaches geography at the Hebrew University of Jerusalem, explains how the spring’s geography helped determine its name. 
 
“The term gihon’ in Hebrew is a derivative of ‘gushing’,” he says. “Due to geologic reasons, the inner cave where the water came from had the shape of a siphon. Therefore, the cave had to be full and then the water gushed out through this siphon tube. Then there was a burst, a gush of the water. Then after a large amount of water flowed out there was a break until the inner cave filled again.”
 
Since Jerusalem is located in a region without many water sources, the spring proved instrumental to the city’s early development. 
 
“Basically, if you want to settle in this area, this is the water source,” Rubin says. “The Gihon. There is no alternative.”
 
Though the Gihon Spring was what Rubin calls “the most important key factor” to the ancient city’s location, another geographic element also proved important. 
 
“The hill itself [on which the City of David was built] could be defended quite easily, because it is a pretty steep hill with valleys on both its eastern and western sides,” Rubin says. “There is desert . . . The only problem where you have to build something is on the north end edge.”
 
Together, Rubin says, the hill and the spring guided Jerusalem’s emergence as an urban center. 
 
“You have water,” he says. “You have land. And, in case of emergency, you have the possibility to defend yourself.”
 
Waterworks
 
The Gihon Spring is located outside the ancient city’s walls. Early residents had to build tunnels to access their water supply when the city was under siege
 
The earliest of these waterworks is Warren’s Shaft—named after British engineer Sir Charles Warren, who discovered the subterranean water system in 1867. 
 
The entrance to Warren’s Shaft is found within the walled portion of the City of David. It is a rock-cut tunnel 41 meters (135 feet) long and has a vertical shaft at its eastern end. The shaft descends 13 meters (42 feet) into the waters of the Gihon Spring. Water could be drawn using a container on a rope. This made it possible for residents to attain water without having to leave the protection of the city walls.
 
The latest—and most impressive—of ancient Jerusalem’s waterworks is probably the so-called Hezekiah’s Tunnel. The construction of the subterranean feature is described in the book of Chronicles in the Bible: “[Hezekiah] blocked up the upper spring of Gihon and brought the water down through a tunnel to the west side of the City of David.”
 
“Hezekiah’s Tunnel was built by King Hezekiah before 701 BCE, when it helped Jerusalem to survive the siege by King Sennacherib of Assyria,” Rubin says. “It is a tunnel cut in the rock beneath the City of David leading water from the Gihon to the Siloam Pool [a freshwater reservoir fed by the tunnel].”
 
The S-shaped tunnel is 533 meters (1,749 feet) long and winds beneath the City of David to connect the spring with a less-vulnerable area of the city. Scientists are not sure why the tunnel curves instead of traveling in a straight line. Some think that workmen might have cut the tunnel to follow naturally curving rock formations, while another theory suggests that ancient engineers might have simply worked to expand a pre-existing crack they discovered into the tunnel. 
 
The Gihon Spring was used by Jerusalem residents throughout the 20th century. 
 
“In antiquity, as far as I know, it was always reliable,” Rubin says. “However, as the city grew larger and larger they had to build other water reserves with large water systems to the houses.”
 
Jerusalem currently gets its water from the area around Rosh Ha-Ain, about 40 kilometers (25 miles) northwest of the city. 
 
Even though the Gihon Spring is no longer vital to the survival of the city, the spring’s subterranean water tunnels are a popular tourist attraction in Jerusalem. 
 
“Today, tourists are going to the springs and to Warren’s Shaft and Hezekiah’s Tunnel every day,” Rubin says. “It’s a wonderful experience in the summer.”
Water Works
The Gihon Spring has been gushing for more than 5,000 years.
Holy Sight
The Pool of Siloam, a freshwater reservoir fed by Hezekiah’s Tunnel with Gihon Spring water, is the reputed site where Jesus cured a blind man.
adjacent
Adjective

next to.

archaeologist
Noun

person who studies artifacts and lifestyles of ancient cultures.

cave
Noun

underground chamber that opens to the surface. Cave entrances can be on land or in water.

Christian
Noun

people and culture focused on the teachings of Jesus and his followers.

construct
Verb

to build or erect.

derivative
Noun

word that is based on (derived) from another word.

development
Noun

construction or preparation of land for housing, industry, or agriculture.

emerge
Verb

to develop or come into view.

engineer
Noun

person who plans the building of things, such as structures (construction engineer) or substances (chemical engineer).

freshwater
Adjective

having to do with a habitat or ecosystem of a lake, river, or spring.

Noun

study of places and the relationships between people and their environments.

geologic
Adjective

having to do with the physical formations of the Earth.

Gihon Spring
Noun

source of water flowing beneath the oldest neighborhood (City of David) in Jerusalem, Israel.

Noun

land that rises above its surroundings and has a rounded summit, usually less than 300 meters (1,000 feet).

instrumental
Adjective

important.

Jewish
Adjective

having to do with the religion or culture of people tracing their ancestry to the ancient Middle East and the spiritual leaders Abraham, Isaac, and Jacob.

Muslim
Adjective

having to do with Islam, the religion based on the words and philosophy of the prophet Mohammed.

religion
Noun

a system of spiritual or supernatural belief.

Noun

natural or man-made lake.

shaft
Noun

underground tunnel.

siege
Noun

organized attack on a fortified or protected structure.

siphon
Noun

pipe or tube with two legs of unequal length, usually ∩-shaped, used to transport water or other fluids over elevations.

Noun

beginning of a stream, river, or other flow of water.

spring
Noun

small flow of water flowing naturally from an underground water source.

subterranean
Adjective

underground.

tourist
Noun

person who travels for pleasure.

urban
Adjective

having to do with city life.

valley
Noun

depression in the Earth between hills.

vital
Adjective

necessary or very important.