In front of the main facade of the San Carlo Theatre there is one of the entrance arches of Galleria Umberto I (the Gallery), that was inaugurated in 1892 as symbol of the new urbanistic planning performed by the Italian Government. It consists of four arms with structure of masonry, covered by a rooftop of glass and iron. The style is the neo-Renaissance chosen by the new Italian State for celebratory buildings, in order to recall the great heritage of the artistic and cultural Age of Renaissance, that was in common among all the small Italian States which Italy was divided into. The top of the dome, that is in the conjunction point of the four arms placed in a cross form, is 57 meters high from the ground and gives to the building a strong appearance of wideness and lightness, strengthened also by the height of the entrance arches.

The Gallery joins the Theatre to Via Toledo, that has been for a long time the most important street in the city of Naples. It was transformed by the Spanish Viceroys, who pulled down the preexisting Aragonese walls (the street was right outside them) and incorporated that street inside new city walls. Via Toledo became soon the heart of the city because it joined the new Viceroy's Palace (the future Royal Palace) and the harbour area with the entrance gates of the city. On its sides all the noble families settled and built their new palaces, while in the empty space between Via Toledo and the new walls the Spaniards built the soldiers' residence (the "Spanish Quarters") with a strictly regular structure still visible nowadays. As time passed they have become popular lodgings.