Treia still preserves some ancient towers of the medieval period: the Mill Tower (late 14th, early 15th century) is a clear example of a fortress built to protect the mill enclosed within from continuous raids and devastations. In Treia, then Montecchio, the Municipality built twenty mills over a 50-year period, in an area which extended only for a few kilometers. Centuries later, Carlo Didimi, mentioned by Giacomo Leopardi, who was a great champion of "Pallone con il Bracciale", Ball and Bracelet sport, worked as a mill inspector. Unlike the other tower in Treia, (the hexagonal Onglavina) the Mill Tower has a quadrangular shape and measures 9.40 per 10.42 meters, 15 meters in height. Besides the well for the mill’s machinery, there used to be two levels which were later divided into more levels or floors made of beams and tiles. On the ground floor were three cereal millstones and the upper floors were used for storage.
Together with the fortification, diagonally opposite, built in the town of Pollenza, it was part of the defensive and control system of the Potenza valley. It was a strong garrison for the bridge located on the border between the two territories and at the crossroads of important routes of communication leading to Treia, Macerata, Urbisaglia and San Severino.