The Republic of Genoa around 1365 built a castle to domain over the Ripa maris below, Finalmarina, so to control Finale and to limit the power of the Carretto marquises. The name of the castle originates from the fact that it wasn’t subject to the control of the local lords and did not have to pay them tributes.

On the beach at its feet there had been for some time active dockyards that produced also large ships for Mediterranean navigation.

Moreover, in the same area the church of San Fruttuoso rose, belonging to the Cavalieri di San Giovanni (Knights of St. John), and was destined to host the pilgrims on their way to the Holy Land.

The medieval fortification can still be recognised in the central polygonal tower that was then incorporated within the Spanish fortress.

During the second half of the 16^th century Castelfranco went through demolitions, reconstructions and frequent occupations by Genoa, both the Spanish and Imperial armies becoming the residence of the royal commissioners. In the end, in 1602, after the death without heirs of Sforza Andrea Del Carretto the last marquis, Finale was occupied by the Spanish crown and became the “Puerta a la mar” of the duchy of Milan.

In the Spanish period (1602-1707) the medieval nucleus was transformed more than once and surrounded by modern fortifications with large bastions. Between 1642-1645 on the ridge above Castelfranco the forts of Sant’Antonio and of the Annunziata were built and linked by a covered road. In 1647 a warehouse for ammunitions and four large barracks were built for the troops that disembarked in Finale.

In 1674-77 Gaspare Beretta and his helper Serena reinforced the Fort of the Annunziata and built new defences on the sea with a ravelin that protected the access to the fortress.

Lastly, around 1680 in the highest part of Gòttero the Legnino Fort was built with large angular bastions.

At the end of the Spanish war of succession (1701-1713) Genoa bought Finale and a few years later started the demolition of the 17^th century fortifications and only Castelfranco was spared from destruction.

The fortress was transformed into a prison and during the First world war it hosted the Austro-Hungarian prisoners, most of which died during the Spanish flu epidemic in 1918-19.

The fortress of Castelfranco currently hosts the Centro di Documentazione Multimediale Storico Territoriale (Multimedia Historic Territorial Documentation centre) with didactic apparatus and multimedia workstations with the reproduction of historical maps, with ancient photographs and postcards dating from the end of the 19^th century and a section dedicated to the history of the Piaggio aviation industry that was active in Finalmarina from 1906 until a few years ago.