Water fixture?

0

Earlier this season, we published a photo of a plastered basin in the north colonnaded building.  In the northeast corner of this room is another water feature, plastered and half-round fed by a water pipe.  Its function is a mystery, in part because we have not yet reached the bottom of the feature.

Fixture.JPG

Christine discovered the feature and below she is seen inspecting and clearing the water pipe.  Ideas anyone?

Christine inspects.JPG