Gihon Spring, just downhill from the ancient city of Jerusalem, was crucial to the survival of its inhabitants, and archaeologists had uncovered the remains of a massive stone tower built to guard this vital water supply. Based on pottery and other regional findings, the archaeologists had originally assigned it a date of 1,700 BCE. But new research conducted at the Weizmann Institute of Science provides conclusive evidence that the stones at the base of the tower were laid nearly 1,000 years later. Among other things, the new results highlight the contribution of advanced scientific dating methods to understanding the history of the region.