This is wall facing of opus signinum for wall 8012. Together with the opus signinum (SU 8263) on wall 8120, this suggests the walls required extra protection. Suggests room I-11 functioned as a cistern or a praefurnium. The fact that it covers wall 8240 suggests this facing post dates that construction.
Taken from the south.
Opus signinum covering S facade of 8012 in room I-1
Photomodel of room I11.