The first wall, completed around the middle of the eighth century, enclosed a surface area of under nine hectares and the surviving documentation and few remains indicate that it must have followed these present-day streets: Pacini, Palestro, Cavour, Buozzi, Curtatone e Montanara, Abbi Pazienza and delle Pappe.
Articulated in a double ring separated by the guards' walkway, the walls were six meters thick at the base and about fourteen meters high, running for a total length of about one kilometer. The first defensive ring must have soon proved insufficient for the city's needs since there is record of buildings being constructed outside these walls as early as the tenth century.
New residential areas developed outside: the oldest of these was San Bartolomeo which grew up around this important abbey as well as other holy buildings whose names reveal their location outside the walls.
Around the third decade of the twelfth century the City Council decided to erect a second set of walls to allow better defence of the city whose perimeter, with respect to ancient times, had more than doubled.
The new walls ran in a sinuous line from Santa Maria a Ripalta to the Ospedale del Ceppo, then turned south following what are today the Chiappettini and Trenfuni streets. They continued south taking in the churches of San Bartolomeo and San Pier Maggiore as far as Santa Maria Nuova, then turned west along what are today the Amendola, Fedi and Gramsci streets, to end once more at Ripaita.
The last circle of walls was built after the great damage caused to the second defensive ring by the Florentines in 1306. The new wall took in the convents of the mendicant orders that had been founded between the late thirteenth and early fourteenth centuries.
The walls were fifteen meters high and three meters thick at the base which decreased to one and a half meters at the guard posts.
Equipped with towers and bastions - the Ambrogi and Thyrion bastions are still visible - the main point of strength was the Medici fortress of Santa Barbara.
Wide moats fed by the Brana and Ombrone rivers completely encircled the perimeter, adding to the defense system that was so efficient that it would never be taken by storm.
Today the third circle of walls is only visible in parts along the present day Matteotti and Arcadia avenues. There were four main gates that allowed entrance to Pistoia from the major cities nearby. Even today those arriving from Florence enter via the Porta Carratica, from Lucca via the Porta Lucchese, from the mountains via the Porta al Borgo, and from Prato - following the via Montalese which is the old Cassia road,via the Porta San Marco. These gates also correspond to the four city quarters that compete for the Giostra dell'Orso.
The walls remained intact until the beginning of the twentieth century when they were knocked down to make way for seemingly better urban development.
Comune di Pistoia