To be more exact, on the least precipitous side, that which looks directly toward Rocca di Cave.
To anticipate any one saying that this scarping is modern, and was done to make the approach to the Via del Colonnaro, I will say that the modern part of it is insignificant, and can be most plainly distinguished, and further, that the two pieces of opus incertum which are there, as shown also in Fernique's map, Étude sur Préneste, opp. p. 222, are Sullan in date.
Fernique, Étude sur Préneste, map facing p. 222. His book is on the whole the best one on Præneste but leaves much to be desired when the question is one of topography or epigraphy (see Dessau's comment C.I.L., XIV, p. 294, n. 4). Even Marucchi, Guida Arch., p. 68, n. 1, took the word of a citizen of the town who wrote him that parts of a wall of opus quadratum could be traced along the Via dello Spregato, and so fell into error. Blondel, Mélanges d'archéologie et d'histoire de l'école française de Rome, 1882, plate 5, shows a little of this polygonal cyclopean construction.