Alessandro de’ Medici ordered its construction in order to defend himself from possible uprisings by the Florentines, at that time recently subjected to Medici power. Built on the basis of a design by Antonio da Sangallo and finished in 1535, the fortress has massive, solid walls. Its forepart facing the city is formed by characteristic diamond-point bosses, alternated with crushed-ball bosses.

A significant example in the history of military architecture, the Fortezza is also one of the first places where Benjamin Franklin’s theories on the electrical nature of lightning were applied in practise. Grand Duke Peter Leopold indeed ordered that the gunpowder warehouses of the main cities of the Grand Duchy should be equipped with large iron bars. The task of fitting the buildings with these bars was entrusted to Felice Fontana who, assisted by Giovanni Fabbroni and in the ambit of the activities of the Museum of Physics and Natural History, conducted important research on electrology.

Today, the Fortezza da Basso is the venue of important international shows like Pitti Immagine, the International Handicrafts Trade Fair and the Furniture Show.