This floor surface, leading into Room 18 to the west across thresholds 5582 & 5583, echoes in its symmetry the crushed tufo floor (SU 5357) that leads into rooms 3 and 4 across the main courtyard to the east. This is one of the interesting aspects of the plan of this part of the terrace, as a gesture toward at least a rough symmetry. Presumably this floor surface marks an area that was covered by a projecting roof from the west, possibly a kind of portico that served as a transition between the interior space of Room 18 and the central courtyard.