THIS winter, the Milanese outpost of the Banca Intesa Sanpaolo’s galleries draws together works from the Brera, the Castello Sforzesco, the Museo Poldi Pezzoli, the Biblioteca Ambrosiana, the Duomo, and farther afield, alongside works of their own, to showcase the inclusive city as a place that down to the 20th century, from the founding of the cathedral in 1386, has welcomed artists from outside, offering them a place to realise their inspiration.

One of the last pieces on show is the plaster bozzetto submitted as a design for the fifth door of the cathedral in a competition in 1955/56 by Lucio Fontana. He used the traditional format of successive narrative panels, but distorted the figures in the style of Rodin’s celebrated “Gates of Hell”. It would have been an exciting statement had his been the winning entry.

The “Genius” of this exhibition’s title is not just the roster of the many foreigners who have made the city what it is — among them, the Florentine Leonardo da Vinci, Donato Bramante from the Marche, and the Venetians Sebastiano Ricci and G. B. Tiepolo — but the genius loci, which is centred on the Duomo.

Visiting the exhibition on St Lucy’s Day (13 December), I was drawn immediately into the light that it shed on how the former imperial Roman capital and later Lombard (Longobard) city came to be dominated by its cathedral. This is the city of St Ambrose (7 December); but it was radically transformed at the end of the medieval period.

Veneranda Biblioteca Ambrosiana, Pinacoteca, MilanJan Brueghel the Elder, Hendrick van Balen, Madonna and Child with a Garland of Flowers (c.1608), oil on panel; oval on copper

The great cathedral, built over two earlier churches for Archbishop Antonio da Saluzzo, was constructed for the Viscontis by German, French, and Bohemian architects and artisans, as local stonemasons did not have the technical skill for a work of such scale. It is built of Candoglian marble, brought by canal on barges from the shores of Lake Maggiore. The Late Gothic structure surged above a sea of brick and timber houses, although its distinctive triangular façade is a much later accretion. Giuseppe Pollack’s 1806 architectonic drawing for it shows how the marble cladding was added to a brick structure. Some of the original stone carvings from the Fabbrica del Duomo have been loaned.

In the first room, we see two statues that at first appear to be a pair, both hewn from Candoglian marble. That of St John the Evangelist was carved, c.1406, by a German sculptor, Walter from Munich. For all the elegance of the folds of his robes and of his long fingers, it is a stiff composition.

Beside it is a slightly later (before 1419) statue of the Syrian Patriarch St Babila. He was martyred in the Decian persecution in 253. Jacopino da Tradate depicts him with three boy martyrs around his feet. Jacopino was Walter’s pupil, but his softer expressiveness, especially on the faces of the individual boys and in the benign expression of the bishop, is light years ahead of him.

Above these larger-than-life figures are four early fragments of stained glass (two prophets with kings David and Solomon) by German and French glassmakers, Cornelius, and Arnold “de Alemagna”, the Savoyard Bartholomew, and William of France (c.1430). Clearly, the cathedral authorities had no difficulty in persuading the Viscontis to allow them to employ skilled foreigners.

Characterful as their faces are, they pale in comparison with the narrative cycle of windows of the life of St John of Damascus by Niccolò da Varallo, following designs by the Brescian painter Vincenzo Foppa (1430-1516). One of the five monks who surround him when he is clothed in the monastery looks out at us while sun floods the upper loggia windows. The perspective might not be quite right, but the way in which the figures are foregrounded is masterly.

Veneranda Fabbrica del Duomo, MilanDog Gargoyle with Leaf Decoration, carved by Annex Marchestem (first decade of the 15th century), Candoglia marble,

Probably the most celebrated artist to become resident here was Leonardo da Vinci (1452-1519). On exhibition is the formal letter of introduction which he submitted to Ludovica Maria Sforza in the 1480s. In it, he lists his accomplishments that might win him service in her household; he enumerates building city defences, designing military equipment, draining land, and canal management. As if by way of afterthought, he adds that he can paint and sculpt, too (Codex Atlantico, f. 108r).

Alongside it is his bird’s-eye view of the city itself, circling around the cathedral, his ink scrawled in a trail as if by a bird’s claw. He annotated it to indicate that the “true” city centre never was the Duomo, but lies underneath the Church of San Sepolcro, across town, which he also drew. If you visit the crypt there, you can walk on the original Roman paving stones of the Forum where the east-west road, the Decumanus, crossed the Cardo, running north-south.

Cardinal Federico Borromeo recognised that the altarpiece that he owned, The Sacred Family with St Anne and the Boy John (c.1520-30) by Bernardino Luini, derived directly from Leonardo’s cartoon, now in the National Gallery in London. Seeing that here with all its Leonardesque flourishes alongside Marco d’Oggiono’s earlier Madonna and Child with John the Baptist and an Angel, I noticed that the attention of both painters showed how thin the claim of the Louvre/Abu Dhabi Salvator Mundi is for the master’s hand.

Fondazione Palazzo ColonnnaJan Brueghel the Elder, Landscape with Pietro del Morrone, Pope Celestine V (c.1593), oil on copper, from the Fondazione Palazzo Colonna, Rome

Borromeo was a discerning patron, attracting artists from Flanders such as Paul Bril and his pupil Jan Breughel. He was determined to make the ducal city into “a little Antwerp”, a Counter-Reformation stronghold close to the Alps, north of which lay so much Protestant misery. In Rome, he had acquired Caravaggio’s Basket of Fruit in the first decade of the new century, hanging it between religious altarpieces and cabinet pieces. Years later, when he wrote a history of his collection (Musaeum, 1625), he recalled how he had for years tried to find a painting its equal that could serve as a pendant, but had failed. Perhaps Fede Galizia’s Glass Stand with Peaches, Quinces and Jasmine Flowers (1607, Cremona) comes closest, but it lacks the hidden iconography of Caravaggio’s masterly work for meditation.

The other great cathedral in any 19th-century city is the central railway station. The train shed of 1864 (in what is now the Piazza Repubblica) was painted by Angelo Morbelli in 1889 in a view reminiscent of Gare St Lazare by Monet. The present building, half a mile further out of town, was designed in 1912 by Ulisse Stacchini, but the final 207m-long building was not completed until 1931. By then, it had grown into the architectural style so beloved by Il Duce, and there is something of an irony that it was in central Milan that, on 29 April 1945, Benito Mussolini and his mistress Clara Petacci were strung up by their heels in front of the petrol station in the Piazzale Loreto.

© Claudio GiustiFrancesco Gonin, Interior of Molteni’s studio in Milan with the Painter and Massimo d’Azeglio (1835), watercolour on paper, Florence, private collection

The city had much expanded; when in 1920 Mario Sironi (1885-1961) painted a series of city views of the industrial sprawl and empty periphery, his compositions adumbrated those of Edward Hopper (1882-1967) with the uncanny and eerie emptiness of streets and highways in the age of the motor car.

Although the Duomo is no longer as visible as the Pirelli Tower next to the central station, it is clearly still at the heart of the imagination for all who know Milan.

“The Genius of Milan” is at the Gallerie d’Italia, Milan, Italy, until 13 March. gallerieditalia.com