The gallery was started in 1865 and opened two years later, though not completed. The style is eclectic, with grotesques, caryatids, pilasters and lunettes, typical of the second half of Milan 19° century. The statues decorating it are by the Milanese sculptor Pietro Magni.
The gallery is mostly commercial: famous and prestigious shops ie libraries here are their locations, as well as popular cafés and restaurants.
In 1859, Milan began to think of a covered walkway linking Piazza Duomo to Piazza della Scala. The left side of the cathedral was built at that time with small buildings and was chosen to rearrange the viability of the center.

The municipality held a public international competition. 176 architects participated and Giuseppe Mengoni won . At the center of the gallery there is a large octagonal "room" gets up to 47 meters high. On the floor there is the heraldic symbol of the Savoia family with a white cross on a red field. Around the sign of the four most important cities in Italy: Turin's bull, the wolf of Rome, the lily of Florence and the red cross on a white field in Milan. In the vault are depicted in mosaic 4 continents Asia, Africa, Europe and America.
The roof of the gallery has a skeleton in iron (353 tons) and the rest in glass. The two main entrances, those of the longer arm, have two great triumphal arches. The iron frame was manufactured in England and assembled in Paris in 6 months.

In 1865 the installation works began with the laying of the first foundation stone by King Vittorio Emanuele II of Savoia, and two years later he opened the gallery, although not completely finished.
Giuseppe Mengoni, the creator of the gallery, died here just falling from the dome during an inspection December 30, 1877.
The gallery, with its coffee quickly became the living room of Milan, and in 1910 the Futurist painter Umberto Boccioni paint the movement of persons in the animated canvas octagonal "Brawl in the gallery."
During 1914 and the first months of 1915, it was the site of demonstrations for the war and anti-war interventionists.
During World War II, in the nights of 13 and August 15, 1943, the gallery was hit by Allied bombing.

For many years after World War II, the area of of thegallery entrance at the side of the Cathedral Square was a meeting place to discuss the relevant facts that characterized the civilian life of the nation . The presence of newsstands and newsboys did gather knots of people, especially at the output time of the newspapers in the afternoon, usually characterized by strong headlines. The years of terrorism did stop the habit of being in gallery to discuss current events.
Symbolically, the Gallery is the agora of the city, the meeting place par excellence. It 's the place that cleanly separates the political power from religious one, but at the same time combines the two founding ideas of human society. It ' a contemporary reinterpretation of the underground cavern used for initiation, which allows today the long and mediated men responding to the demands of civil society and the religious, between the two institutions which the sacred have been materialized in.