Plate-Level is treated as ground-level by the citizens of Romerus. Romerus is built on top of a cluster of older cities, seperated from the ruins by large plates and pillars holding up the new city. Plate-level has walkways for traveling on foot, as well as access to Trams . In certain areas, it even has access to The Under , but that's supposed to be blocked off and it's illegal to sneak into it.
Plate-level typically refers to the bottom plate, but can be used in refference to the plate most closely represented by the mathematical floor function.