The fortress that dominates the medieval town of Montecarlo is also known as Rocca del Cerruglio from the name of the oldest fortifications that stand on the site. The first military complex, with a triangular plan, was probably born between the 12th and 14th centuries, when the fortified village did not yet exist, founded in 1333 at the behest of the powerful and nearby Lucca and of Giovanni and Carlo di Boemia (hence the name of Montecarlo), who came to the aid of the Lucchesi against the Florentines. Until that moment in another area of the hill stood the Castle of Vivinaia, the residence of Countess Matilde di Canossa, destroyed by the Florentines in 1332-33 during the flight due to the arrival of Giovanni and Carlo, whose remains are today under the current cemetery, just outside the village and the city walls. From a definition taken from some documents of the time we learn that the Cerruglio was a soqquadrato Gothic building surrounded by a strong wall of squared stones and equipped with a stronghold of forts.