From Project Athinai
The South Stoa was built around 425 BC along the South side of the Agora, facing North.
The stoa was probably used by the bankers who installed their tables under its portico. Like the Tholos, it was also used to store standard weights and measures. The rooms were probably dedicated to official administrative bodies.
The stoa, made mostly of poros, stood on a high terrace compensating for the northwest downslope of the terrain. It consisted of a row of 15 rooms behind two aisles created by two rows of poros Doric columns, an inner one in the middle of the building and an outer one forming the facade of the stoa. The inner and lateral walls were made of sundried brick on a poros base. The rear wall, made entirely of poros, also served as a retaining wall for the 6 m wide east-west road running in the back of the stoa.
Rooms were almost identical. Only the central room differs from the other: it was accessed through an anteroom. These rooms were probably used as dining rooms, accomodating seven couches each. This is attested by the layout of the fifth room from the east which had a slightly raised border floored with pebble-studded cement, like contemporary dining rooms. The doors of these rooms were slightly off centre to the east.
Another stoa was built a few centuries later in the same area. Archaeologists designate the older one as "South Stoa I" and the latter as "South Stoa II".
American School of Classical Studies at Athens; The Athenian Agora: A Guide to the Excavation and Museum, 1990
Camp, John M.; The Archaeology of Athens, Yale University Press, 2001, pp. 127-128
Connolly, Peter and Hazel Dodge; The Ancient City - Life in Classical Athens & Rome, Oxford: Oxford University Press, 1998
Travlos, John, Pictorial dictionary of Ancient Athens, Books that matter, New York, 1971, p. 534