Even in First Temple times approximately 3,000 years ago, water cisterns were painstakingly chiseled into the rock, then coated with sealing layers of yellow waterproofing plaster to form substantial underground reservoirs. When a cistern of this type was discovered near the Temple Mount in 2012, it proved that the Gihon Spring, though useful, was not an adequate source of water for Temple needs.I noted the discovery of this cistern (I think) in 2012 here and of the 2005 playground cistern here (when another was found in the same area in 2019).[...]
I also noted the discovery of the section of the Lower Aqueduct to Jerusalem in 2015 here and of the High-Level Aqueduct in 2010 here.
For more on the work of Sir Charles Warren, see here and links.
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