Forte Michelangelo is the squat, hexagonal Renaissance fortress that anchors the seaward side of Civitavecchia's harbour. Pope Julius II della Rovere commissioned it in 1508 to defend the papal port from Barbary pirates and (more pressingly) from the French. Three architects worked on it in succession: Bramante began the design, Antonio da Sangallo the Younger continued the bastions, and Michelangelo completed the central keep under Paul III. The fortress survived both the bombing of 1943-44 and centuries of subsequent neglect, and is one of the very few Renaissance military structures in Italy still essentially intact.
The fort is owned by the Italian Navy and only opens to the public on occasional guided tours and during specific events — check the local tourist office. Most visitors content themselves with the exterior, which is impressive enough: an 80-metre-square keep ringed by lower curtain walls, with a moat that has been replaced by gardens. The best photograph is from the harbour side at sunset.