"From the phot. and description, p. 555, this appears to be a built pithos, rather than a cistern." [deposit nb] Grid 30/ΙΔ also mentioned ... 28 July-3 August 1931
Cistern-system west of the Stoa of Zeus. Two chambers connected by a tunnel, each with two fills. Lower fill in south chamber contemporary with upper fill in north chamber, at the end of the 4th c. B.C ... Ca. 375-160 B.C.