http://agathe.gr/guide/late_roman_fortification_wall.html
Late Roman Fortification Wall East of the East Building and Mint we arrive once again at the Panathenaic Way, which in this area is lined along its eastern side by a massive wall built in the 3rd century ... The wall was constructed in the years following the sack of Athens by the Herulians in A.D. 267; it starts at the Acropolis with a new gate, runs north down the east side of the roadway, takes in the ruins of the Stoa of Attalos, and then turns eastward toward the Library of Hadrian. The old Agora, former center of town, is not even within the fortified limits of the Late Roman town, which lay to the east.