The Aterno originates from the alluvial basin of Montereale at about 800 m. It comes from the outflows of the massif which culminates in Mount Civitella on which the watershed dividing the Aterno basin from the Vomano one is located. The spring area consists of a large number of pools, rivulets and streams: that is why it is difficult to locate. Going further downstream we find the water mills. Of the many existing in the valley, however, only two of them work, thanks to the current of the river near Pizzoli. Upstream from the town of Raiano, the course of the river narrows, thereby offering a fascinating landscape, due to its impervious shape. Leaving the gorge of San Venanzio and after a couple of kilometers, upstream from the town of Popoli, it joins the Sagittario river: there you have the Pescara river.