Western wall of room 2 and eastern wall of room 1, the extent of which appears to be original on all sides. The eastern facing retains plaster finishing. Plaster finishing on western facing in room 1 suggests interior wall. The section of rubble and concrete preserved at the mid-point of the wall, to which the highest standing section of plaster adheres, suggests that this wall may have been rebuilt in a second phase, after the higher courses of ashlar blocks were spoliated. This phase may be related to opus incertum walls 5311 and 5343 to the south.