Together with the Cassero Senese, it is one of the two surviving architectural elements from the 14th-century city walls, having endured the extensive reconstruction work carried out by the Medici in the late 16th century.

Renamed Porta Reale, it served as the sole entrance to the city for over two centuries, central to all major roads.

This modification, remembered by a plaque on the outer walls of the bastion, was initiated by Prefect Stefano De Maria di Casalnuovo, after whom the square outside Porta Vecchia is named.

Below the gate are two plaques: one commemorates the partisans who fell during the liberation of the city, and the other recalls the 1328 siege of Grosseto.

However, the latter contains a historical error, attributing the defense of the city to Bino degli Abati del Malia, who had actually died about ten years earlier.