The first traces go back to a papal bull of 920, where Pope John X authorized the construction of a fortification to protect the church from the incursions of the barbarians and the eruptions of the heretics. Thanks to this intervention, the city developed rapidly, becoming the most important inhabited center of the area.

Subsequently, the castle was also reinforced and strengthened, erected on a large square-shaped artificial embankment, with eight large towers to support it. The invasion of the Hungarians and the barbarian raids led to the construction a few years later also of the walls around the city.

In the following centuries, the walls lost their symbolic value and became support for housing construction, thus neglecting maintenance, also due to the crisis of the Venetian Republic. And then after a propitious period of the city, the wars of the sixteenth century arrived, which highlighted the inadequate defensive structure, also given by the rapid evolution of military techniques and artillery.

Little remains of the powerful keep today, including the famous Torre Donà, particularly characteristic for its slope, is today one of the tallest Italian towers of medieval origin, with its 52 meters high. The Grimani Tower, also called Torre Mozza for its collapsed upper part, and which in the past was to be the most important element.

The Torre Pighin, erected in 1138 and among the few to survive along the Rodigo urban walls. The 14th century Roncale Tower is now part of the Roncale palace, from which it takes its name. And finally the Porta San Bortolo, built between 1482 and 1486, which is characterized by its medieval architecture.