Forte Michelangelo, Renaissance fort in Civitavecchia port, Italy.

Forte Michelangelo is a rectangular Renaissance fortress of about 100 by 82 metres at the southern end of Civitavecchia's harbour, its walls clad in travertine blocks. Four round corner towers, named San Paolo, San Pietro, San Romolo and San Giulio, stand at the corners, and an octagonal keep dominates the north flank. A chapel dedicated to Saint Fermina stands inside.

Julius II laid the cornerstone himself on 14 December 1508; Donato Bramante began the work, continued by Giuliano Leno and Antonio da Sangallo the Younger. The fortress was finished in 1535, the octagonal keep by 1537. Its name comes from a local tradition, unsupported by documents, that Michelangelo designed the keep.

The fortress chapel is dedicated to Saint Fermina, Civitavecchia's patron saint, who according to tradition found refuge in a cave on this spot. The four corner bastions carry the names San Paolo, San Pietro, San Romolo and San Giulio, after the apostles and early Roman martyrs.

The fortress's inner courtyard is accessible on weekends, though visiting hours are limited and can change based on port operations. It's best to check ahead since the harbor authority uses the premises and may restrict access on certain days.

The octagonal keep, the Maschio, is attributed by local tradition to Michelangelo, though no document confirms his involvement; the name of the fortress rests on this claim. The oak tree of Julius II's coat of arms on the east tower marks where the pope laid and blessed the cornerstone on 14 December 1508.