The Medici fortress of Santa Barbara is a significant example of military architecture of the sixteenth century, around which the names of Nanni Unghero, Sanmarino and Bernardo Buontalenti are intertwined. The construction of the Pistoia fortress is part of Cosimo I's territorial policy, but its origins are earlier and date back to the early decades of the fourteenth century, during the dominion of the Florentine Republic; Some elements of this season are still clearly legible - such as the large central tower with the functions of a keep - later incorporated into the Renaissance construction. The new fortification was begun in 1543, at the behest of Cosimo I, by Giovanni d'Alessio d'Antonio, known as Nanni Ungaro, and then continued by another great military engineer of the sixteenth century, Giovanni Battista Bellucci, known as Sanmarino, to whom owes the definition of the internal quadrilateral, with bastioned fronts articulated by the rafters with the gunboats. A few decades later, Cosimo I himself entrusted Bernardo Buontalenti with the expansion of the fortress, who built a large bastion that encloses the previous fortress; the Buontalentian addition planimetrically incorporates the quadrilateral of Nanni Ungano, joining the city walls and placing the pre-existing fortress on a kind of pedestal, a real stronghold. From the mid-seventeenth century, the Pistoia fortress experienced a slow and gradual decline, to later become a barracks and a military prison, finally recurring in the most tragic pages of city life. In 1944, during the Second World War, four young Pistoians were shot there. The Monumental Complex of the Fortress of Santa Barbara is one of the places whose events are most closely linked to the history of the Pistoian Risorgimento. The central tower of the Fortress, which was the prison in which the Pistoia patriots were imprisoned between 1848-1850, preserves graffiti, writings and drawings in black charcoal and red sanguine made by imprisoned patriots. A plaque commemorates the shooting of Attilio Frosoni, a patriot from Pistoia who was executed by the Austrians on 29 June 1849.