Italy's geography: a peninsula with a mountain wall at the top

What the shape actually is

Italy comprises a mainland section at the top of a long peninsula, plus two large islands and many smaller ones. The territory sits between latitudes 35° and 47° north and longitudes 6° and 19° east, and covers 302,068 square kilometres, of which about 7,210 square kilometres is water.

The Alps join Italy to the central-western part of the European continent and form the entire northern boundary, running about 1,000 kilometres. The Apennines rise south of the Po Valley and run the length of the peninsula from Liguria to Calabria, continuing into northern Sicily, over about 1,350 kilometres.

So the country has two mountain systems arranged perpendicular to each other: one across the top, sealing it from the north, and one down the middle, dividing every part of the peninsula from every other part at right angles to the coast.

Almost 40% of Italian territory is mountainous on the broader definition, and the flat quarter is not distributed evenly. Most of it is the Po Valley, surrounded by the Alps to the north, east and west.

Why the coast outweighs the borders

Italy's land frontier is modest and its maritime one is enormous, and the ratio is the point.

Against that, the coastal development of the peninsula and the islands runs to about 8,000 kilometres. A country whose land borders total under two thousand kilometres and whose coast runs four times that is a country oriented towards the sea, and every port city on this list, from Venice to Genoa to Naples, was independently powerful for exactly that reason.

The position does something else. Italy sits between Europe and Africa and functions as a bridge between them, which is a geographic description rather than a political one and has been true through every period of the country's history.

Where the flat ground is

The Po Valley is the largest continuous plain in Italy and it does a disproportionate share of the country's work.

Geographers separate continental Italy from the peninsula along a line drawn from La Spezia to Rimini, taking in the southern flank of the Alps, the Po Valley, Liguria and the Apennines north of that line. The line marks a real break. North of it the ground is flatter, wetter, connected to Europe through the alpine passes and able to carry heavy industry. South of it none of those four things holds.

Much of the Italian soil is the product of human work as well as geology. The record describes terrain that is partly mountainous, partly hilly, partly volcanic, partly lagoon-edge, with land dried out by reclamation schemes at Circeo, Ferrara and Comacchio among others. Where Italy has flat farmland at sea level, somebody usually drained it.

What the Po Valley carries

The valley is worth a section of its own because a single plain holding a quarter of a country's flat ground determines where that country's economy sits.

It is enclosed by the Alps to the north, east and west, which means its climate is continental rather than Mediterranean: colder winters, hotter summers, more fog and far more reliable rainfall than the peninsula south of it. It is watered by rivers descending from two mountain systems at once, the Alps on three sides and the Apennines to the south, which gives it a volume of fresh water no other part of Italy has.

It also has the passes. The alpine crossings that connect Italy to central Europe all deliver into this valley, so goods moving between the Mediterranean and the industrial north pass through it by necessity rather than by choice.

Put those three together, flat ground, reliable water and the only land route to Europe, and the concentration of Italian industry in the north stops being a historical accident and becomes the obvious outcome. Any economy operating on this territory would have made the same choice.

The cost is that everything else is somewhere else. The peninsula south of the La Spezia to Rimini line has narrow coastal strips, a mountain spine down the middle, less water and no land border with anybody. Its natural orientation is towards the sea and towards north Africa, which is what it has historically been oriented towards.

What the volcanoes are doing

Italy is one of the few European countries with active volcanism, and the reason is the same convergence that raised the Apennines.

The Aeolian archipelago north of Sicily holds the clearest examples: Lipari, the largest; Vulcano, now almost extinct; Panarea; and Stromboli, an eruptive cone that has been in more or less continuous activity for as long as the record covers.

The geological ages of the two mountain systems differ and explain their shapes. The Alps formed during the Mesozoic and Cenozoic; the Apennines formed during the Oligocene, which is later. The younger, softer range runs down the peninsula and carries the seismicity; the older, harder one stands across the top.

A country built on a convergent margin has earthquakes, and Italy's are concentrated along the Apennine spine rather than in the north.

The islands sit inside the same system.

How the Apennines organise the peninsula

The spine is the feature that does the most work and gets the least attention.

Running from Liguria to Calabria over about 1,350 kilometres, the Apennines divide the peninsula lengthwise, so that almost every point on the east coast is separated from the corresponding point on the west coast by a ridge. Crossing the peninsula has historically been harder than travelling along either coast, and travelling along either coast has historically been easier by sea than by land.

That has three effects that recur throughout Italian history. Coastal cities developed facing outward, because the sea was their cheapest connection to everywhere including to each other. Inland communities developed in valleys and basins that were defensible and self-contained. And no single power based on one coast could easily control the other, which is why the peninsula supported several substantial states simultaneously for most of two thousand years.

The range is also younger and softer than the Alps, formed in the Oligocene rather than through the Mesozoic and Cenozoic, and it carries the country's earthquakes. A settlement pattern built along a seismic spine is a settlement pattern with a recurring problem, and the historic centres of central Italy have been rebuilt more often than their appearance suggests.

What the mountains do to the weather

Two ranges at right angles produce a climate map more complicated than the latitude suggests.

The Alps block the northern air and hold the Po Valley's weather in, which is why a basin at the same latitude as central France behaves continentally: cold winters, hot summers, persistent winter fog. The peninsula south of the Apennine watershed gets Mediterranean weather, mild and wet in winter and dry in summer, and the two coasts of the peninsula differ from each other because the spine between them intercepts the weather crossing it.

Altitude then does what it does everywhere. A country spanning 35° to 47° north would have a wide climate range on latitude alone; adding a thousand kilometres of alpine border and thirteen hundred of Apennine spine gives it a vertical range on top, so that permanent snow and subtropical coast exist inside the same borders.

The islands add a third element. Sicily and the smaller southern archipelagos sit far enough south to be genuinely North African in their summer climate, which is the practical meaning of the country functioning as a bridge between two continents.

Sardinia and Corsica together divide the Tyrrhenian Sea from the Sardinian Sea, which is a way of saying that the western Mediterranean is partitioned by Italian and French territory.

Sicily is the peninsula's continuation rather than a separate object: the Apennines run into its northern edge. Sardinia is geologically distinct, older, and was never connected to the mainland in the way Sicily nearly is.

The smaller archipelagos matter more than their size suggests. They carry the volcanism, they carry a disproportionate share of the endemic species, and they carry the harbours that made the medieval maritime republics possible.

Where the water is and is not

Italy has more water than a Mediterranean country would be expected to have, and it is distributed unevenly.

The Po and the rivers feeding it drain a basin enclosed by two mountain systems, so the north has year-round flow from alpine snowmelt as well as rainfall. The peninsula has neither in the same quantity: its rivers are shorter, steeper, and far more seasonal, running hard in winter and sometimes to nothing in summer.

The consequence is agricultural before it is anything else. Rice, maize and dairy farming belong to the north because they need reliable water. Olives, vines and drought-tolerant crops belong to the centre and south because those are what the rainfall there supports. The two halves of Italian cooking that visitors notice, the butter-and-rice north and the oil-and-wheat south, are a direct readout of where the rivers run.

Reclamation extended the usable area at the margins. The schemes at Circeo, in the Ferrara district and at Comacchio dried lagoon-edge ground into farmland, and where Italy has flat land at sea level it is generally land somebody drained. That is worth stating because it means the country's agricultural map is partly an engineering decision rather than a natural endowment.

What the geography decided

Three consequences follow from the arrangement above, and all three are visible in the rest of this catalogue's articles on Italy.

The country is hard to unify and easy to divide. A spine of mountains running the length of a peninsula puts every coastal region closer to the sea than to the region on the other side of the ridge. That is why the city-states developed as they did, why unification took from 1848 to 1870, and why regional identity remains as strong as the history article describes.

The north and the south are different places physically before they are different economically. The Po Valley is a large, flat, well-watered plain adjoining the industrial heart of Europe through alpine passes. The south is mountainous, drier, and adjoins the sea. An industrial economy will locate itself in the first, and did.

The sea is the country's frontier. With 8,000 kilometres of coast against under 2,000 kilometres of land border, Italy's exposure is maritime. That has determined its trade, its migration, its defence problems and its relationship with north Africa for as long as there has been a state here, and it is not something any government has been able to alter.

The high point is Mont Blanc at 4,806 metres, on the French frontier at the top of the alpine wall. The low point is Contane at three metres below sea level, in the reclaimed ground of the Po delta. Between the two lies almost everything the country is.