Conceived on the basis of designs by many artificers (Bernardo Buontalenti, Giovanni Cantagallina, Vincenzo Bonanni, Giovanni de’ Medici), the massive "New Fortress" was built astride the 16th and 17th centuries. Though built later, it was part of the great project for Livorno as city-fortress that Grand Duke Francesco I de’ Medici commissioned from Buontalenti. Part of the Fortezza Nuova was demolished (including the curtain wall joining it to the Fortezza Vecchia or "Old Fortress") in 1629 to permit the construction of the picturesque quarters of Venezia Nuova and San Marco, ordered by Grand Duke Ferdinando II de’ Medici.

The Fortezza Nuova presents a polygonal plan and a well-structured interior, which is entered from the bridge on the docks. It was used for military purposes until the end of World War II. Following various uses, in 1972 it was restored by the Commune of Livorno, and the upper part was made a public park.