The Carnic Alps are divided by the Gail valley into the South Carnic group and the northern Gailtal Alps.
This expansion of mainland territory was followed in 1420 by the acquisition of Friuli after a successful war with the emperor Sigismund, thus bringing the possessions of the republic up to the Carnic and Julian Alps, their natural frontier on the north-east.
The tract adjoining this long line of lagoons is, like the basin of the Po, a broad expanse of perfectly level alluvial plain, extending from the Adige eastwards to the Carnic Alps, where they approach close to the Adriatic between Aquileia and Trieste, and northwards to the foot of the great chain, which here sweeps round in a semicircle from the neighborhood of Vicenza to that of Aquileia.
This, with the exception of a brief tenure of Cremona (1499-1512), formed her permanent territory down to the fall of the republic. Her frontiers now ran from the seacoast near Monfalcone, following the line of the Carnic and Julian and Raetian Alps to the Adda, down the course of that river till it joins the Po, and thence along the line of the Po back to the sea.
Along the coast-line, roughly speaking between the Apennines at Rimini and the Carnic Alps at Trieste, three main systems of lagoons were thus created, the lagoon of Grado or Marano to the east, the lagoon of Venice in the middle, and the lagoon of Comacchio to the south-west (for plan, see Harbour).
The country south of the Drave is occupied by several groups of the southern limestone zone, namely the Carnic Alps, the Julian Alps, the Karawankes and the Steiner Alps.