In narrating this event, Polybius gives a detailed description of the town: Psophis ... is situated in the central parts of the Peloponnese, in the western corner of Arcadia, and adjoining the Achaeans dwelling furthest towards the west.
On the western side of the town there is a rapid torrent, impassable during the greater part of the winter, and which ... makes the city exceedingly strong and inaccessible.
The banks of the Erymanthus are precipitous, but not very high; and between them and the steep summit of the hill upon which the town stood there is a small space of level or gently-rising ground.
The summit is a sharp ridge, sending forth two roots, one of which descends nearly to the angle of junction of the two streams, the other almost to the bank of the Erymanthus at the eastern extremity of the city.
While the Macedonians were attempting to scale the walls in three separate parties, the Eleians made a sally from the gate in the upper part of the town.
The town walls followed the crest of the ridge to the north, and the bank above the two rivers on the opposite side; and at least up through the 19th century they were traceable nearly throughout the entire circuit of the place.
On the north-eastern side of the town, which is the only part not protected by the two rivers or by the precipices at the back of the hill, there was a double enclosure surrounding the citadel, although this has since entirely disappeared.