On the west its boundary is the sea, which on this part of the coast forms but few and indifferent harbours.
On the north it imperceptibly merges into the broad hill-land of Etruria.

The region thus enclosed forms a magnificent plain traversed by the Tiber, the "mountain-stream" which issues from the Umbrian, and by the Anio, which rises in the Sabine mountains.
Hills here and there emerge, like islands, from the plain; some of them steep limestone cliffs, such as that of Soracte in the north-east, and that of the Circeian promontory on the south-west, as well as the similar though lower height of the Janiculum near Rome; others volcanic elevations, whose extinct craters had become converted into lakes which in some cases still exist; the most important of these is the Alban range, which, free on every side, stands forth from the plain between the Volscian chain and the river Tiber.
Here settled the stock which is known to history under the name of the Latins, or, as they were subsequently called by way of distinction from the Latin communities beyond the bounds of Latium, the "Old Latins" (-prisci Latini-).

But the territory occupied by them, the district of Latium, was only a small portion of the central plain of Italy.

All the country north of the Tiber was to the Latins a foreign and even hostile domain, with whose inhabitants no lasting alliance, no public peace, was possible, and such armistices as were concluded appear always to have been for a limited period.
The Tiber formed the northern boundary from early times; and neither in history nor in the more reliable traditions has any reminiscence been preserved as to the period or occasion of the establishment of a frontier line so important in its results.

We find, at the time when our history begins, the flat and marshy tracts to the south of the Alban range in the hands of Umbro-Sabellian stocks, the Rutuli and Volsci; Ardea and Velitrae are no longer in the number of originally Latin towns.