From Fermo to Ascoli, a province recently divided, the Tenna and Aso are before, one the boundary with the province of Macerata, to the north, then the other, the Aso (in ancient times Asis) forms the Valdaso that delimits the administrative boundary between the provinces of Ascoli Piceno and Fermo, and is well known for the fertility of its land, cultivated mainly with peaches.
This latter, at the source, passes through Montemonaco, Comunanza, Force, Rotella, Montedinove, Montalto, Carassai, Montefiore dell'Aso; toward the Adriatic Sea, it flows crossing for the whole two municipalities of the province of Fermo: Campofilone and Pedaso. On the left side, according to the course of the waters, all the municipalities of the northern bank, belonging to the province of Fermo: Montefortino, Montefalcone Appenino, Santa Vittoria in Matenano, Montelparo, Monte Rinaldo, Ortezzano, Monte Vidon Combatte, Petritoli, Monterubbiano, Moresco, Lapedona, Altidona. The Tenna is born in the municipality of Montefortino, in the province of Fermo, and crosses the southern Marche and more specifically the Tenna Valley, crossing for most of its course, the province of Fermo.
The source is located between Priore Mount and Sibilla Mount, in the heart of the Sibillini mountains, part of the central Apennine system. After a few kilometres the Tenna enters in the Infernaccio Gorges of the Apennines of Umbria-Marche. The centres lapped by the river are: Montefortino, Amandola, Smerillo, Santa Vittoria in Matenano, Servigliano, Falerone, Belmonte Piceno, Montegiorgio, Grottazzolina, Magliano di Tenna, Rapagnano, Fermo, Monte Urano, Sant'Elpidio a Mare and Porto Sant'Elpidio, all in the province of Fermo.