The division of Italy into suitable regions for the purposes of description presents many problems and the enormous variety of both physical and human conditions makes it possible to devise dozens, even hundreds of distinct units. The question of choosing suitable regions is avoided and Italy is divided into four main areas, North, Centre, South and Islands. These are further subdivided on the basis of the 19 regioni. The choice of the regioni as the basis for description does not imply that any abrupt change is encountered along their boundaries. Unlike the provinces, they have not even had any administrative function until very recently. Except where separated by sea ( Sardinia, Sicily) or by mountains ( Liguria) they merge imperceptibly into one another and in their description, therefore, excessive adherence to their precise boundaries must be avoided. Many Italian geographers have used the regioni and with some justification at least, since statistical data are readily available for them. Before proceeding with the description of each regione, however, it seems opportune to distinguish some basic regions in the country so that the reader will not later lose sight of simple, fundamental contrasts, which of course bear no relationship to the limits of the regioni. The main geographical regions of Italy based on a consideration of both relief and economic activity. The order in which they, are treated in the following summary is entirely arbitrary.
1. The Alps. These are the highest and most rugged part of Italy. The cultivation of crops is extremely limited and farming is dominated by dairying on the basis, mainly, of natural pastures. More than three-quarters of the hydro-electricity produced in Italy and much of the timber come from the region. Thanks to the need to cross the Alps at various points, there are several important routeways, using the main valleys and helping to reduce the isolation of many of the less-accessible valleys. Industry is limited to a few localities and there are no large towns. Tourism flourishes in some areas.
2. The North Italian Lowland. Flat or gently sloping, fertile and in places irrigable, this is Italy's most productive agricultural area. A very large proportion of the lowland is under field crops, but emphasis varies from one part to another. Wheat, maize, livestock fodder crops, rice, sugar beet, vegetables and vines are all grown in one part or another, and yields are much higher than elsewhere in Italy. Previously without minerals of more than local importance, the lowland has now become Italy's chief source of natural gas and is covered by western Europe's most extensive pipeline system. Away from region 3 there are a number of manufacturing concentrations: apart from Trieste, Venice and Bologna, all distinguished on the map, Vigevano, Pavia, Verona, Vicenza, Padua, Modena, Parma and Ferrara are all more than simple commercial and administrative centres.
3. Industrial north-west Italy. Roughly within the area distinguished, manufacturing overshadows agriculture in terms of employment. Italy's most highly industrialised communes lie along an axis following the foot of the Alps between Turin and Brescia. Industrial settlements spread from this line both up valleys (e.g. behind Bergamo) and into the lowland away from the foothills ( Turin and Milan are both some distance from the Alps). The largest number of industrial centres is between Milan and the Alps, while Milan with certain adjoining communes has half a million persons in manufacturing and Turin over a quarter of a million. In this region there is a total population of about 7m inhabitants and a large proportion of Italy's textiles, engineering goods, chemicals and high grade steel are produced here. Milan is the financial and commercial capital of Italy.
4. Ligurian Riviera. This narrow mountain-backed strip of land is so distinct that it must be separated from neighbouring areas. Agricultural land is very limited but very productive. There are three major ports, including Italy's largest, Genoa, and some manufacturing, especially at Genoa (about 100,000 persons). The tourist industry of the region enjoys worldwide fame.
5. Mountains of the Peninsula and Islands. This region is divided among so many regions in Chapters 11-13 that it is important here to point out some characteristics found throughout. Though of widely differing types of rock (mainly sandstone in the north, limestone in the centre and crystalline in the extreme south and Sardinia) the Apennines and the mountains of the Islands are everywhere lower than the Alps and less of a barrier to movement. For their general altitude (1,500-2,500 metres) they are very rugged, however, and steep slopes, poor soils and low rainfall in the summer months (in spite of quite a high annual total) make them less productive on the whole than the Alps. Natural pastures are poorer, forest growth more limited and the hydro-electric potential much more restricted. As in the Alps, crop farming is not widespread, but the Apennines do have more cultivable valleys and basins, especially in the central part. There are no large towns in the region and very few industries, but several trans-peninsula railways pick their way across.
6. Hills and Lowlands of the Peninsula and Islands. Except where the mountains extend to the coast itself they are usually flanked by hill country, lower, but in places still very broken. Coastal lowlands and interior basins, though important locally, are limited in area. Soil conditions vary enormously and the most fertile and very densely peopled lands have been distinguished as region 7. Region 6 generally has only a moderate density of population, while in places (notably in southern Tuscany and much of Lazio, in Basilicata and in much of Sardinia) it is thinly populated. Almost everywhere yields of the principal cereal, wheat, are low, while in places conditions are only suitable for the vine and the olive. Livestock farming is limited, extractive industries are confined to a few areas and there are hardly any large-scale industries.
7. a-d. Four particularly productive and densely peopled parts of the Peninsula and Sicily have been distinguished. The Arno valley between Florence and the sea has about 1½m people (mixed farming, considerable manufacturing), the Naples area about 3½m (vegetables, fruit, cereals, limited manufacturing), Bari and the Salentine Peninsula about 2½n (wine, olives, very limited manufacturing), and the fertile coastlands of southern Calabria and northern and eastern Sicily about 2½m (citrus fruits, wine, very limited manufacturing).
8. Rome. The national capital forms a concentration of some 2 million persons quite out of proportion to the resources of the poor area in which it is located. As well as being the seat of national government it is a religious and tourist centre of international significance.
9. a-j. In addition to Milan, Turin and Rome, which are important enough to form special regions of their own, ten other communes with over 250,000 inhabitants have been distinguished, since most if not all are major regional centres, too large to be accounted for merely in terms of local needs. All except Trieste and Messina clearly occupy a high level in the Italian urban hierarchy through their considerable spheres of influence and many functions.