The Tesino flows in the province of Ascoli Piceno. It winds for 37 km, and passes through the districts of Force, Rotella, Montedinove, Castignano, Montalto delle Marche, Cossignano, Offida and Ripatransone, and it flows into the Adriatic at Grottammare.
The Tronto is the most important and well-known river (Pliny the Elder mentions it as the Truentum). It starts from Monti della Laga (where it marks the border between Abruzzo and Lazio) then, after flowing to the north of the Amatrice basin, it enters the Marche and changes direction to the East and arrives at Arquata del Tronto. Straight afterwards it collects the waters of other tributaries such as the Fluvione torrent that starts at the top of Monte Vettore, from the right the Volpara torrent that rises from Macera della Morte (East side), passes through a gorge and it skims Ascoli Piceno, where near the town centre it is reached by its main tributary, the Castellano (45 km long) coming from Lepri Peak.
The Tronto feeds several hydroelectric power plants. From the Comune of Castel di Lama to the mouth, the river marks the border between the Marche and Abruzzo. It flows into the Adriatic between San Benedetto del Tronto and Martinsicuro.
During the Napoleonic era it gave the name to the Department of Tronto which included the present provinces of Ascoli, Fermo and Macerata and whose capital was the town of Fermo.