The Medicean Fortress, located on the Colle di San Donato (viale B. Buozzi) in Arezzo, is an example of a defensive military architecture of the 16th century. The building, perfectly inserted into the wall and the irregular pentagonal system to fit the ground with bastions of different setting and shoe of considerable height in comparison to the lead wall, rises at the top of the meadow of the Prato. The Fortezza castles are a panoramic spot on the city, the Arno Valley, the Pratomagno Massif and the Catenaia Alps. The Medici citadel probably rises on the area of the ancient medieval citadel, which dates back to the 9th or 10th centuries. Certainly it is known that in 1319, during the fortification work of the city, was built the Cassero of San Donato, which was seriously damaged by the town revolt against Bishop Guido Tarlati and that in 1343 the arches demolished the fortress, then rebuilt in 1344, and between 1384 and 1398 the fort was again demolished and rebuilt by the Florentines, in the meantime they became the owners of the city. During the revolt of 1502 against the Florentine rule, the aretines tried to break down the fortress. The Republic of Florence gave orders, however, to reconstruct it according to the principles of the fortification to the modern, entrusting the work Giuliano and Antonio da Sangallo. This fortress, however, was damaged around 1530. The actual fortification is the one built, respecting in part the original designs by Giuliano and Antonio da Sangallo between 1538 and 1560 by order of Cosimo I de 'Medici. The work was directed by Antonio da Sangallo il Giovane. During the construction, the Palace of the Commune was destroyed with the adjoining Torre Rossa, the ruins of the Palace of the Captain of the People, the Tarlati Palace of Pietramala and about 17 churches in addition to all the old turbulent old town of the 14th century ancient city, Etruscan city and the Roman Forum. The military motivation was to clear the field with artillery strikes that could be directed from the fort against the city to prevent anti-Florentine revolts. In the place was created a slope that was filled with the ruins of houses and palaces, called Prato. The work absorbed part of the previous building: the new building, with three doors open, was surrounded by a large moat, and included the Belvedere, the Spine, the Diacciaia ramparts on the western flank and the interior spaces (rooms, galleries , wells and air intakes). At the beginning of the nineteenth century, French troops tried to blow up the Fortress with the mines (the effects of the explosion are still visible on the west side); in 1868 it was first restored. The Fossombroni family acquired the fortress in the mid-nineteenth century. In 1893, by the will of Henry Henry, he became the owner of the Commune. It was adapted to garden and walk to the public with several works performed in the period 1896-1904. Inside one of the ramparts, a 14th-century fortress gate was found, adorned with a statue of St. Michael the Archangel, now preserved in the museums of the city. After a new restoration, on June 24, 2016, the fort was returned to the city; on the occasion, archaeological excavations have brought to light the ruins of the church of San Donato in Cremona, dating back to the year 1000, and a mosaic floor covering a Roman-era building.