Located outside the Medicean walls in the immediate area beyond Porta Nuova, the square is officially dedicated to the brothers Carlo and Nello Rosselli but is commonly referred to as "della Vasca" ("of the Basin") due to the semicircular fountain at its center, which effectively serves as a traffic roundabout.

The Cosimini industrial workshops appeared nearby in 1874, and in 1896 a monument to the fallen of Italy's unification wars was erected.

In 1932, the Liberty style Villa Barth was replaced by Angiolo Mazzoni's Post Office Building.

After World War II, in 1945, the square was named after the anti-fascist brothers Carlo and Nello Rosselli.

[2] In 1970, Palazzo Cosimini was replaced by a modern concrete multipurpose building by Ludovico Quaroni, breaking with the square's original style.