(criterion IV)
An integral part of the city’s historical context, the circuit of walls, which remains clearly legible for around 9 kilometres, significantly reflects the evolution of more than two centuries of military architecture. Along the perimeter of the urban walls it is possible to read the successive construction phases and their associated technical and formal features which, taken together, provide a compendium of the different solutions in military engineering developed in each historical period.
Begun in the 12th century and subsequently modified in step with the various phases of development of the urban core and with the changing defensive needs of each era, the walls preserve to the south the medieval curtain walls along the former course of the River Po and, to the north, the complex Renaissance defensive system designed by Biagio Rossetti as part of the grand programme of urban expansion known as the Addizione Erculea. In the stretch between the Torrione del Barco and the Torrione di San Giovanni, eleven semicircular towers survive from Rossetti’s project and, crowning Corso Ercole I d’Este, stands the Porta degli Angeli gate, which acquired its present form in 1526.
In the southern section of the walls, the typical elements of the alla moderna bastioned defensive system can also be identified, such as the bastions commissioned by Alfonso I in the 16th century and the remains of the citadel erected during the years of papal rule, of which several bulwarks survive today.
Following a major restoration campaign, during which numerous work sites succeeded one another over a decade from 1988 onwards, the walls today – together with the green belt that surrounds them – form one of the most distinctive features of Ferrara’s urban landscape.
The walls of Biagio Rossetti and Alessandro Biondo
di Andrea Marchesi
The Peace of Bagnolo, signed on 7 August 1484, put an end to the armed conflict that for more than two years had set Ferrara against Venice. Duke Ercole I d’Este was forced to relinquish his rule over the Polesine of Rovigo, which had already been invaded in May 1482 by Venetian troops that repeatedly crossed the Po frontier and even advanced to within a few hundred metres of the ducal castle. The killings, looting, fires and destruction wrought by the enemy in the hunting reserves of the Barco ducale, in the palace of Belfiore and in the church of Santa Maria degli Angeli dramatically exposed the defensive vulnerability of the suburbs north of the medieval wall that followed the line of today’s Corso Giovecca and Viale Cavour: a vast, wholly undefended area. To protect it, during the war the duke ordered the construction of emergency fortifications, in particular timber bastions and high earthworks at the points nearest to the walls. Out of this bitter defeat and the fear that hostilities with the Republic of St Mark might resume, Ercole d’Este decided to launch one of the most ambitious programmes of urban renewal in Europe, based on the construction of an imposing new circuit of walls. This enabled Ferrara to double its size with new streets, palaces and churches, reaching a surface area comparable with that of the greatest Italian cities, such as Bologna, Florence, Naples and Milan.
On 25 August 1492 work officially began on the expansion, known in historiography as the Addizione Erculea. Three days later excavation started on the moat, which began in the west at the church of San Marco in the Borgo di Sopra, described an irregular arc that took in the renowned residential and ecclesiastical buildings in the suburbs north of the castle, and finally joined the north-eastern corner of the old city in the Borgo di Sotto. The undertaking appeared colossal: it involved constructing a fortified barrier more than five kilometres long that would bring within the city more than 250 hectares of land, when the entire extent of the medieval quarters did not reach 180. At the same time the new streets were being laid out and the earthworks raised, and at the beginning of June 1495 the ducal steward Antonio Maria Guarnieri was able to conclude a first contract for the building of the walls. These were entrusted, as a private commission, to the engineer Biagio Rossetti (1444–1516), who acted as contractor in partnership with the city’s leading kiln-owner and brickmaker, Alessandro Biondo, his co-father-in-law. Chroniclers date to 1497 the completion of the two city gates of San Benedetto and San Giovanni Battista at the ends of the decumanus of the new extension (the old via dei Prioni, corresponding to today’s Corso Porta Po–Corso Biagio Rossetti–Corso Porta Mare), while the Porta degli Angeli to the north, at the end of the street of the same name (now Corso Ercole I d’Este), only reached its definitive form in 1525.
The construction of the walls had major repercussions on economic and social dynamics, as well as constituting an extraordinary laboratory of technological and engineering knowledge. This was applied, for example, in the manufacture of mechanical devices for lifting water, moving earth and transporting millions of bricks from the kilns. In the municipal accounting records of Ferrara for the years 1493–1494, the “inzignieri” Siacho da Nizza, his son Onorato and Sante Novellini frequently appear as designers of various drainage structures equipped with horse-driven waterwheels, later built by specialist carpenters (marangoni) such as Paolo dall’Olio, Giacomo Dianti, Antonio dal Bondeno and Girolamo Zuccola.
By imposing quite unprecedented workloads, Ercole called in an exceptional number of peasants from the Ferrarese, from Romagna, the Modena area and the Reggio area to work on the project. This gave rise to (vain) protests both from those whose land within the construction site was expropriated, and from the very large proportion of his subjects – including members of religious orders and prostitutes – who were forced to bear the burden of the taxes and levies imposed to finance the extraordinary line of fortifications.
The “Rossettian” walls built between 1492 and 1505 mark the transition from vertical, plunging defence to horizontal or “grazing” fire, and represent one of the most distinguished examples of the “transitional” phase of Italian military architecture preceding the later bastioned system. A water-filled moat, not deep but very broad (between 35 and 80 metres), made any attempt to approach the low, thick, battlemented curtain walls more difficult. These had a these had a talus at the base (scarpa), marked by a decorative braided stringcourse. The smaller semicircular towers are set at intervals equal to half the range of small arms and, as they served to defend the enceinte through the cross-fire of crossbows and small artillery pieces, they were equipped with merlons (now lost) and with lateral loopholes on two levels, the upper of which was reached by timber platforms. Internal movement of troops from one tower to another was ensured both by the wall-walk along the top of the walls, protected by the battlemented parapet, and by the counterscarp at the foot of the earthwork, on the upper part of which (known as the ramparo) further heavy long-range weapons were emplaced.The duke’s keen interest in the progress of the works on the walls and of the building activity within the Terra Nova is borne out by the documentary evidence itself, which gives us the image of a true “architect-prince”, ready to engage and debate with scholars and designers in order to find the best solution for each individual work. Standing out among these figures are the engineer Biagio Rossetti and the humanist Pellegrino Prisciani, a fine connoisseur of the writings of Vitruvius and Leon Battista Alberti. Recent archival research has revealed that between 1493 and 1497 the ducal financial administration (Masseria camerale) supplied numerous quires of royal-format paper to the duke, to Rossetti and to Prisciani expressly “to make drawings”: this circumstance – a graphic activity carried out, as it were, by six hands – sheds new light on the conceptual and design genesis of the entire Addizione Erculea.