SU 5528 is comprised of at least 3 (most likely more) avertine blocks covered in places with mortar. In the North 5520 continues under the concrete foundations for later wall 5362 and seems to be abutted by 5529 and 5536 (which sit atop wall 5437 and block 5438). To the West and South SU 5528 continues under un-excavated stratigraphy (i.e., under pavers 5496), in fact a small hole bellow collapsed block 5464 to the South reveals what looks like the continuation of this feature. the construction suggests it my be the cover of a deep drainage system that might be associated with earlier features 5437, 5438, and the initial monumentalization of the area.