East of Ferrara lies the Po Delta, an expanse of marshland and lagoons where the River Po splits into several channels, trickling to the sea, and small fingers of land poke out into the Adriatic. Etruscan traders set up the port of Spina here between the fourth and third centuries BC, when the sea covered much of the land from Comacchio to Ravenna. Partly owing to drainage schemes, the briny waters have since retreated by 12km, and the area becomes a bit less marshy each year – an advantage for local farmers but a threat to the many varieties of sea and shore birds that inhabit the area. The two main lagoons of Valli di Comacchio and Valle Bertuzzi together form a major part of the Parco del Delta del Po (w parcodeltapo.it), which with the surrounding wetlands now constitute one of Europe’s most highly regarded birdwatching areas, providing a habitat for nesting and migrating birds, including heron, egret, curlew, avocet and tern.