On the E end of the SU, the level of the drain is flush with the height of floor slabs (SU 5668) and thus the drain in this area seems to have been visible and part of a walking surface. At the W end of the SU, where we have no slabs abutting the drain slabs and the bedrock surrounding it is high and irregular, it is not so clear that the drain would have been part of a visible pavement surface.

These carefully worked concave slabs would have served as a drain to control water within this middle terrace of the complex. Water from west and east met at the small, regular, circular hole in these slabs, and drained into an underground channel.