Warren's Shaft

Warren's Shaft is an archaeological feature in Jerusalem discovered in 1867 by British engineer Sir Charles Warren (1840–1927). It runs from within the old city to a spot near the Gihon Spring, and after its 19th-century discovery 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. In 2005, archeologists discovered the ruins of a pair of walls that would have protected the overland path to the spring prior to the tunnel's construction.

• http://en.wikipedia.org/wiki/Warren's Shaft