The original toponym of the town , dated 1151, was Castrum Montis Marie. In the eighteenth century and in the nineteenth century it was transformed in Monte Cassiano, becoming Montecassiano afterwards.

The castle walls, built starting from 1403, encloses the typical historical center, which can be accessed only through one of the three doors. These are known as St. Giovanni, Armando Diaz and Cesare Battisti.

The heart and the most scenographic place of Montecassiano remains the Square “Unità d’Italia”. The square is flanked in the north by Palazzo of Priori, in the west by Palazzo Compagnucci, and in the east by the facade of the church of St. Marco and by the former Convent of the Augustinians. Between Palazzo of Priori and Palazzo Compagnucci a spectacular staircase, framed by a wide arch, leads to the Collegiate church of St. Maria Assunta.