This pile of sandstone boulders was once a large vertical section of cliff, known as Threatening Rock.
It was separated from the cliff by wind and water erosion probably long before construction work on Pueblo Bonito began,
and stood out away from the cliff very much as does the rock near the water tank.
The Native Americans, fearing the collapse of the rock, constructed at its base a series of short walls to reduce erosion of the soft sandstone rather than to support the rock.
It is here that the only remaining portion of those walls is found.

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