The earliest inhabitants of Praeneste needed first of all, safety, then a place for pasturage, and withal, to be as close to the fertile land at the foot of the mountain as possible.  The first thing the inhabitants of the new city did was to build a wall.  There is still a little of this oldest wall in the circuit about the citadel, and it was built at exactly the same time as the lower part of the double walls that extend down the southern slope of the mountain on each side of the upper part of the modern town.  It happens that by following the edges of the slope of this southern face of the mountain down to a certain point, one realizes that even without a wall the place would be practically impregnable.  Add to this the fact that all the stones necessary for a wall were obtained during the scarping of the arx on the side toward the Sabines,[31] and needed only to be rolled down, not up, to their places in the wall, which made the task a very easy one comparatively.  Now if a place can be found which is naturally a suitable place for a lower cross wall, we shall have what an ancient site demanded; first, safety, because the site now proposed is just as impregnable as the citadel itself, and still very high above the plain below; second, pasturage, for on the slope between the lower town and the arx is the necessary space which the arx itself hardly supplies; and third, a more reasonable nearness to the fertile land below.  All the conditions necessary are fulfilled by a cross wall in Praeneste, which up to this time has remained mostly unknown, often neglected or wrongly described, and wholly misunderstood.  As we shall see, however, this very wall was the lower boundary of the earliest Praeneste.  The establishment of this important fact will remove one of the many stumbling blocks over which earlier writers on Praeneste have fallen.

It has been said above that the lowest part of the wall of the arx, and the two walls from it down the mountain were built at the same time.  The accompanying plate (III) shows very plainly the course of the western wall as it comes down the hill lining the edge of the slope where it breaks off most sharply.  Porta San Francesco, the modern gate, is above the second tree from the right in the illustration, just where the wall seems to turn suddenly.  There is no trace of ancient wall after the gate is passed.  The white wall, as one proceeds from the gate to the right, is the modern wall of the Franciscan monastery.  All the writers on Praeneste say that the ancient wall came on around the town where the lower wall of the monastery now is, and followed the western limit of the present town as far as the Porta San Martino.

Returning now to plate II we observe a thin white line of wall which joins a black line running off at an angle to our left.  This is also a piece of the earliest cyclopean wall, and it is built just at the eastern edge of the hill where it falls off very sharply.