By far the larger portion of Northern Italy is occupied by the basin of the Po, which comprises the whole of the broad plain extending from the foot of the Apennines to that of the Alps, together with the valleys and slopes on both sides of it.
In this part the Apennines are separated from the sea, distant about 30 m.
The Roman district, the largest of the four, extends from the hills of Albano to the frontier of Tuscany, and from the lower slopes of the Apennines to the Tyrrhenian Sea.
Parma, one of the finest cities of northern Italy, lies in a fertile tract of the Lombard plain, within view of the Alps and sheltered by the Apennines, 170 ft.
One chief result of the manner in which the Apennines traverse Italy from the Mediterranean to the Adriatic is the marked division between Northern Italy, including the region north of the Apennines and extending thence to the foot of the Alps, and the central and more southerly portions of the peninsula.