This is A small structure made of concrete and faced with petit apparel. It sits in the corner between 8237 and 8232, and seems designed to support the wall covering arch 8237. This suggests that room I-11 his a substructure in the building, perhaps a drain or furnace. This seems to belong to the original phase of the construction of the building.
Taken from the east.
E-W wall (N) bound to 8237 and 8232 in room I-11; E-W wall (S) bound to 8237 and 8233 in room I-11