http://agathe.gr/guide/southwest_area.html
Southwest Area - Industry and Houses Leaving the area of the boundary stone, one can head southwest up a valley leading toward the Pnyx, meeting place of the Athenian assembly. Here are the complex remains ... The Poros Building at the top (north) has been tentatively identified as the State Prison. The other walls and wells represent private houses dating from the 5th century B.C. to the Byzantine period. ... It has been suggested that this might be the State Prison (desmoterion), where Sokrates and others convicted of political crimes were executed. ... The Poros Building, possibly the State Prison, seen from the north, 5th century B.C.