The Fortress of the Girifalco with probable Etruscan origins was a post used by the Goths first and later by the Lombards at the time of the Barbarian invasions. Yet, news about it dates to 1258, only, thanks to an act of conveyance of the complex bought by Arezzo.

In the years, it underwent numerous alterations and restructuring that started in 1266 and continued in the XVI century as established by the Casali who were the lords of Cortona for all the XIV century. The Sienese carried out a further reinforcement work when they were allied with the inhabitants of Cortona in the battle against Arezzo and the local Guelfs. Yet, the Florentines, who owned the fortress since 1411, performed the most important structure that gave the fortalice its current architectural appearance.
In the XV century, the central body of the fortress was carried out and also Cosimo I de' Medici worked on it at the half of the XVI century. After a long inspection on all the fortresses that had recently come into the possession of Florence, the Grand Duke was astonished by the peculiar position of the Cortona's stronghold. Thus, he decided to transform it into one of the most imposing bulwarks of the Medicean power in the territory of Arezzo. Even if Florentine money financed this work, started in 1556, the local population strongly contributed to it since they were submitted to heavy taxation.
The new castle showed a trapezoidal perimeter of walls surrounding it and four huge bastions dedicated to St. Margherita (in effect, the church titled to her, who is Cortona's patron saint, rises at a short distance), Santa Maria Nuova, St. Egidio and St. Giusto. The post of the garrison, the powder magazine and the prison are on the inside. Moreover, the walls were built with cutting-edge methods with a terreplein at their foot planned to soften the gunshots.
The town immediately benefited from the new restructuring that allowed it to defend from the pressure of the Sienese and of the State of the Church, having its borders not far from Cortona's. the new atmosphere of peace and stability that started in the XVII century, the Grand Dukes' interest in military constructions began to weaken to the benefit of luxury residential palaces and the stronghold progressively started to lose its importance. Therefore, the Fortress of the Girifalco became the base of a small garrison that acted as a town police, only.