In 1590 Ferdinando I commissioned Bernardo Buontalenti to build the fortification called Forte di San Giorgio to protect the city from the high, but in particular, it was used to hold the Medici treasury, which was preserved in a secret hiding place made into the hill. Its perimeter started under Belvedere's wall from Porta S. Giorgio, "in Pitti's Garden". The fortress was completed in 1595 reaching Arcetri's hillock. It is situated at an altitude of 75 m. and, for this reason it is not so vast if compared to the Fortezza da Basso. The fort was connected to Palazzo Pitti and Palazzo Vecchi with secret passages through the Giardino di Boboli and the Corridoio Vasariano.
This enclosed walkway between the two palaces allowed the Medici to wander between the two without any problem, in the same way, they could avoid epidemic as it happened during the 17th century when the plague infected the city's population or else, it could provide a shelter for the Gran Duke if the city came under attack. Forte Belvedere's star-shaped plan is not perfectly symmetric. It is supported by four main bulwark and other two minor bulwark were built at different altitude.
The main doorway features the Medici's family coat of arms. The Palazzina's smooth plastered walls inside the fortress were built previously by Bartolomeo Ammannati. On the ground floor, there is an open-gallery loggia facing the hill. The graceful clock above the central part of the villa was added during the 18th century. Although the fort was called Fortezza di Santa Maria, the Florentines have always called it Forte Belvedere for its beautiful view.
From here no one never fired or was shot at during the war. The outdoor as well as the interior of the Palazzina (villa) are today used for art exhibitions.