The Forte Michelangelo complex extends over a vast Roman building from the imperial age. The quadrilateral plan is protected at the coners by four cylindrical towers and by the octagonal keep that looks towards the port. The fort has imposing dimensions, with a rectangular plan and four enormous coner towers and an octagonal keep.

The majestic building was commissioned by Julius II, to make Civitavecchia the main port of the Papal States. The architect Donato Bramante was appointed, who asked for advice on the design of the fort from the greatest expert of the time, Leonardo Da Vinci. Pope Della Rovere was followed by other pontiffs, up to Paul III, who inaugurated the structure. Bramante was succeeded in directing the works by his pupil, Antonio da Sangallo, but later, to finish the construction, the Renaissance master par excellence was called: Michelangelo Buonarroti. The multifaceted artist took over the project when the complex was only missing the keep. He applied his unmistakable traits: the purity of the forms, devoid of any useless onament, and the overhang of the conice.