There is a simple expedient by which a conception of the topography of the country about Praeneste can be obtained.  Place the left hand, palm down, flat on a table spreading the fingers slightly, then the palm of the right hand on the back of the left with the fingers pointing at right angles to those of the left hand.  Imagine that the mountain, on which Praeneste lay, rises in the middle of the back of the upper hand, sinks off to the knuckles of both hands, and extends itself in the alternate ridges and valleys which the fingers and the spaces between them represent.

EXTENT OF THE DOMAIN OF PRAENESTE.

Just as the modern roads and streets in both country and city of ancient territory are taken as the first and best proof of the presence of ancient boundary lines and thoroughfares, just so the territorial jurisdiction of a city in modern Italy, where tradition has been so constant and so strong, is the best proof for the extent of ancient domain.[2] Before trying, therefore, to settle the limits of the domain of Praeneste from the provenience of ancient inscriptions, and by deductions from ancient literary sources, and present topographical and archaeological arguments, it will be well worth while to trace rapidly the diocesan boundaries which the Roman church gave to Praeneste.

The Christian faith had one of its longest and hardest fights at Praeneste to overcome the old Roman cult of Fortuna Primigenia.  Christianity triumphed completely, and Praeneste was so important a place, that it was made one of the six suburban bishoprics,[3] and from that time on there is more or less mention in the Papal records of the diocese of Praeneste, or Penestrino as it began to be called.

In the fifth century A.D. there is mention of a gift to a church by Sixtus III, Pope from 432 to 440, of a certain possession in Praenestine territory called Marmorata,[4] which seems best located near the town of Genazzano.

About the year 970 the territory of Praeneste was increased in extent by Pope John XIII, who ceded to his sister Stefania a territory that extended back into the mountains to Aqua alta near Subiaco, and as far as the Rivo lato near Genazzano, and to the west and north from the head of the Anio river to the Via Labicana.[5]

A few years later, in 998, because of some troubles, the domain of Praeneste was very much diminished.  This is of the greatest importance here, because the territory of the diocese in 998 corresponds almost exactly not only to the natural boundaries, but also, as will be shown later, to the ancient boundaries of her domain.  The extent of this restricted territory was about five by six miles, and took in Zagarolo, Valmontone, Cave, Rocca di Cave, Capranica, Poli, and Gallicano.[6] These towns form a circle around Praeneste and mark very nearly the ancient boundary.  The towns of Valmontone, Cave, and Poli, however, although in a great degree dependent upon Praeneste, were, I think, just outside her proper territorial domain.