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These two stones are part of the inverted siphon is composed of individual stone blocks that are carved out and then are joined with a "collar sleeve" arrangement. Collar and sleeve joint are sealed using a hydraulic plaster and olive mash paste. They are on display at the Israel Museum.
This is one of the few preserved sections of a sealed "inverse siphon" that is located on the western side of Bethlehem. This is a sealed siphon so that water flows from a higher point on the south of Bethlehem, down into this depression, and the up to a higher elevation.