In 1538, as part of the revisions to the State defensive system ordered by Cosimo I de’ Medici, work began on the fortress and the new walls of Arezzo, under the direction of Antonio da Sangallo the Younger who utilised the drawings of Giuliano (1502) and Antonio the Elder (1505).

The Medici stronghold rises on the hill of San Donato on an area first occupied by buildings in the 3rd – 2nd century B.C., and then by a keep in the 14th century. It is an interesting example of sixteenth-century military architecture for its plan in the form of a five-pointed star, the rationality of its structures, and the innovation of architectural solutions. A peculiar feature of the walls instead consists of the considerable height of the scarp compared to the plumb wall. Dismantled in 1800 by the French, the fortress was restored in 1868 and successively reworked several times. At the end of the 19th century, Count Enrico Falciai Fossombroni willed the fortress and bordering land to the Commune of Arezzo so that it should be used for common good.

Today a public park, the area around the Medici fortress offers a beautiful panorama over the city, the plain, the Arno river valley and Pratomagno.