Italy's biggest lakes, on three measurements

Lake Garda is the largest Italian lake by surface, 369.98¹ sq km, and by volume, 49 cubic km, but the deepest is Lake Como at 410³ m, so the answer changes with the measurement you pick.

The criterion: three measurements, and three separate tables

Every lake below is ranked on three published measurements from an institutional source, and on nothing else. Surface, maximum depth and volume are three different questions, and merging them into one "biggest lakes" list is how most rankings go wrong.

The sources are not uniform, and that matters more than the ordering. Garda comes from the Comunità del Garda, Maggiore from CIPAIS, Como and Iseo from the 2004 OLL report, Bolsena from the Lazio water plan confirmed by ARPA Lazio, and Trasimeno from two Umbria region publications that contradict each other.

By surface: Garda, then a long gap

Garda covers 369.98¹ sq km, or 143 sq miles, which is more than Maggiore and Como put together.

Two of those rows are soft. Trasimeno has no single figure, and Bolsena's own source writes its surface as an approximation. CIPAIS itself publishes both 212² and 212.5² sq km for Maggiore on two different pages; the detail sheet gives 212.5², which is the number used here.

By depth: Como wins, and Trasimeno is not in the race

Como reaches 410³ m, 1,345 feet, and Trasimeno reaches 6 m at its deepest point.

Maggiore is the odd one here: it is not the deepest at its deepest point, but it has the greatest mean depth of the six, 176² m against 155³ m for Como. A lake can be deep everywhere or deep in one trench, and those are different lakes to swim in.

The frequently repeated line that Como is the deepest lake in Italy, or in Europe, is not in any source we could read. What the 2004 report supports is narrower: deepest of the large prealpine lakes.

Garda is either 346 m or 350 m deep

Two Italian institutional sources give Lake Garda two different maximum depths, and this page is not going to pick one. The Comunità del Garda, the body that brings together the lakeside municipalities and provinces, publishes 346¹ m. The first OLL report of 2004, produced by the Lombardy region with ARPA, Fondazione Lombardia per l'Ambiente and CNR-IRSA, publishes 350¹ m.

Four meters is not a rounding artifact, and neither body has corrected the other. We record 346¹ m as the primary figure because it comes from the authority closest to the lake and is more recent, and we keep 350¹ m visible because it is the figure that appears in the comparison table with Como and Maggiore.

The limnological database of CNR-IRSA would be the independent check. Its server resolves but the connection times out, so the confirmation does not exist yet.

By volume: two lakes have no published figure

Garda holds 49 cubic km of water, Maggiore 37.5², Como 22,500³ million cubic meters, which is 22.5 cubic km, and Iseo 7,600⁵ million cubic meters, which is 7.6.

Bolsena and Trasimeno publish no volume at all in the sources used here. That is not a small gap: without volume you cannot compare a shallow wide lake with a deep narrow one on the only measure that matters for water quality, which is how much water there is to dilute what goes into it.

Trasimeno: two figures from the same regional authority

Trasimeno's surface is 128⁷ sq km on the Umbria region's park page and 124⁷ sq km in a PDF published by the same body. Its water surface elevation is not published by any institutional source we could open, and ARPA Umbria sits behind a challenge page we did not work around.

So Trasimeno appears in the surface table as a range and is absent from the volume table. It is the clearest case on this page of a lake that everybody describes and nobody measures in public.

What the numbers change when you are standing there

Garda's water sits at 65 m above sea level and Bolsena's at 305⁶ m, which is most of the reason the two lakes feel like different climates. Como sits at 198³ m and Iseo at 186⁵ m.

Depth is the other thing you feel. At 410³ m, Como's water column never warms through; at 3 to 6 m, Trasimeno is warm by June and turbid after wind. Then the shape. Garda has 158.4 km¹ of shoreline enclosing 369.98¹ sq km of water; Como has 170 km³ enclosing only 145³ sq km, folding back on itself with a sinuosity index of 3.98³. That index, not the distance, is what predicts your driving time.

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