South Stoa II did not stand alone. It formed one wall of an ambitious project: the South Square, a long enclosed courtyard built at the south end of the Agora around the mid-second century BC. The Middle Stoa ran parallel along the north, the East building closed the eastern end, and the older Aiakeion and Southwest Fountain House sealed the west - the latter fixing the angle for the whole complex. South Stoa II shut the south side. At 93 meters it was longer than the building it replaced, a single Doric colonnade of thirty columns in hard gray poros, facing north into the courtyard. The columns stood unusually far apart, and screen walls between them closed off the two ends, a typical Hellenistic touch. A small fountain sat in a vaulted niche in the back wall, fed by an aqueduct buried under the street behind.

Constructing the new stoa meant destroying the old. South Stoa I, the shabby mudbrick dining hall that had served Athens' magistrates since the late 5th century BC, stood directly in the way. South Stoa II was laid out on a different orientation - dictated by the Aiakeion - and at a lower level, so the builders cut down into the bedrock and wiped out every trace of the western half of the earlier building. The pottery packed into the new foundation trenches dates the work to the mid-second century. The whole thing went up cheaply and quickly, which the borrowed material made possible. Up to thirty years may have passed between the demolition of the Square Peristyle and the day its stones rose again here, waiting in storage for their second use.

What happened inside is genuinely unsettled, because the purpose of the whole South Square is debated. One school of thought, led by Homer Thompson and R.E. Wycherley, reads the complex as an expansion of the lawcourts that met in the neighboring Aiakeion - which would make this stoa a place where juries gathered for trials. The discovery of allotment machines, the devices used to select Athenian jurors at random, in the adjacent Middle Stoa lends that idea weight, as does evidence that the earlier Square Peristyle had also served as courts. The excavator John Camp leaned the other way, toward an older view that the square was meant for commerce - in which case the stoa held shops rather than jurors. Justice or trade: the building has not yet said which.

South Stoa II had a short life. It was torn down and the ground given over to workshops before the first century AD - probably wrecked by the damage Athens suffered when the Roman general Sulla sacked the city in 86 BC. True to the building's own history, its fragments went on to other lives: pieces were hauled off to construct the Library of Pantainos around 100 AD. Iron smelters worked the site until the mid-first century AD, then marble sculptors took over. Early in the second century AD even the back wall was rebuilt, this time to retain an aqueduct along the Agora's edge. The remains stayed buried until 1959, when excavations led by Homer Thompson finally reached the level of the stoa that earlier digs had passed straight over.