This is a wall of opus signinum that lines the northern facade of wall 8120. It survives on the lower portion of the wall only. Together with opus signinum 8264, which lines wall 8012 in room I-11, this suggests the walls in this room required extra protection, from water (if a cistern) or smoke and fire (if a praefurnium).
Taken from the north.
Opus signinum covering N facade of 8120 in room I-11
E-W wall (S) of room I-11, in NW quadrant of area; N-S wall (W) of Room I-12, W of wall 8120; Opus signinum covering N facade of 8120 in room I-11.