E-W running wall E of tufo paving slabs and bound to N-S running wall 4057. Tufo, ashlar, and rubble construction. W corner broken off, but probably abutted or covered tufo slabs 4055. Same construction as wall 4057, with which it seems to form a boundary between the tufo slabs to the W and the not-yet-fully excavated area to the north and the not -yet-fully excavated area to the SE. Function and relationships still uncertain.