- The Maremma was the most prominent alluvial plain in Etruria proper, bounded to the north by the Colline Metallifere; these uplands, as the name suggests, were an important metal ore zone, which projects into sea, with Elba (another metal ore source) at its maritime limits. The whole region is composed of four river basins; the largest, the Ombrone (the fourth largest of the peninsula), is accompanied by three smaller rivers, the Albegna and the Fiora to the south and the Bruna to the north. The Albegna (67 kilometers long in a catchment of 737 square kilometers) forms an important physiographic divide between northern and southern Etruria and is the most studied valley of the region. The valley was thus an important feature of Etruscan political geography, providing a self-contained buffer zone and a means of communication into the interior. A prominent characteristic feature of the coastal margin of this river valley is the lagoon that runs from Ansedonia to Pescia Romana and the poor drainage promoted by sediment transport from higher in the valley that blocks the exit to the sea. Another prominent feature is the high promontory of Monte Argentario, which protects the lagoon from the sea approaches. Behind the lagoon there are also some low, isolated hills that stand above the surrounding alluvial plain; together with a hill zone backing onto the high mountains, these complete the key ecological zones of the valley.
Historical Dictionary of the Etruscans. Simon K. F. Stoddart.