Castellaccio, an ancient castle of the Counts Guidi of which there are documents dating back to 925, is located a few minutes from Tredozio. Of the majestic structure there are only ruins and some underground rooms used as cisterns.
The keep has a rather imposing appearance: it was built with solid walls in lime and stone, the shape was octagonal and was flanked by a tall tower 17, the Church of S. Maria Maddalena and the Casa del Conte. In the mid-nineteenth the Castrum Treudacium had already become a ruin.
