It’s told that, in the eleventh century, Matilde of Canossa erected a tower called “Mastio di Matilde”, to defend and guard the coast.
In the fourteenth century a square plan fortress, the so-called “Quadratura dei Pisani”, was built around the tower in its defense. Later on, in 1505, Antonio da Sangallo the Elder, was commissioned by Cardinal Giulio de’ Medici to design a new additional fortification, that had to include the Tower and the “Quadratura”.
The Fortress comes with a pentagonal plan, has mighty brick walls and is surrounded, except on one side which is now a square, by the Medicean Canals, the waterways crossing the old city center.
During the Napoleonic invasion in 1796, the ramparts were largely restored by French soldiers, and slits for guns were inserted.
The fortress was badly damaged by bombing in 1943, which caused a large crack in the curtain wall.