Like Serravalle, Faetano and Montegiardino, it became part of the Republic of San Marino in 1463. Its coat of arms features three red flowers, like the three peaks on which the ancient castles of Torricella, Fiorentino and Pennarossa stood. The ruins of the last two can be seen along the Castellaccio path. Of the ancient medieval fortress of Pennarossa (named after the colour of the rock on Monte Moganzio) some ruins remain, such as the two ancient cisterns dug into the rock. Monte Carlo saw the success of an epic feat performed by the aviator Gianni Widmeer, who landed his monoplane plane there in 1913.
Pennarossa Castle, on Mount Moganzio, is a very ancient site; its construction dates back to the early years of the year 1000. The fortress was purchased by the San Marino people in the first quarter of the 17th century, but it was probably already dilapidated and abandoned at the time of annexation. Nearby is the site of the Castellaccio di Fiorentino, with which it is connected by forest paths along the Toro ditch.
Perched between two limestone hills overlooking sharp gully ridges and the dense vegetation of the Fosso del Toro, on the southern slope of Fiorentino Castle, a steep path offers unusual views, "moments" of wild nature and also the interesting historical and archaeological evidence of the ruins of the CASTELLACCIO (13th-14th centuries).