At that time, Gian Galeazzo Visconti, duke of Milan from 1351 to 1402, was establishing relationships with a number of Tuscan merchant families to improve the finances of the duchy.

[1] The first generation of Borromeo bankers in Milan named as their heir the son of their sister, Margherita, who had married into the distinguished Vitaliano family of Padua.

He was very successful in his mercantile and banking affairs and also served Duke Filippo Maria Visconti (ruled 1412-47) as state treasurer and counselor; for this, he was awarded the title of Count of Arona in 1445 and was given a large amount of property outside Milan; the family at one time possessed the entire area around Lago Maggiore.

In 1916 they were created princes of Angera by King Victor Emmanuel III of Italy, a title still held by the head of the Borromeo Arese family.

[5] In fact, until the 18th century, the term "palace" was only given to homes of rulers or government buildings; all others, large or small, were called case (houses).

Substantial additions were made to the Casa Borromeo in Vitaliano's time, but the original late Gothic facade was retained; it has undergone several modifications through the centuries (most notably after bomb damage in World War II).

The columns forming porticoes in the courtyards (severely damaged in 1943 and restored) are short and sturdy, carved from serizzo (a type of granite), with capitals of large, stylized leaves; they also carry pointed arches and echo the shape and proportion of the main portal.

The brick wall of the palazzina was plastered and painted with a colorful repeating pattern of a count's coronet, groups of rings (a heraldic motif), and the Borromeo motto, humilitas (humility).

[11] When the restoration of Casa Borromeo took place in the 1950s under the direction of architect and archaeologist Ferdinando Reggiori, a number of fresco decorations were found inside the palazzina.

[13] During the 19th century, the Borromeo Arese art collections were installed in the building for public display,[14] and for a time the back section of the house served as the Direzione Generale (headquarters) of the Milanese police.

In 1495/1500, sculptor Cristoforo Luvoni carved a lunette over the main door of the church depicting the Virgin and Child between father and son, Vitaliano and Filippo.

[16] To the right of the church's entrance, a copper statue of 1691 by Dionigi Bussola depicts Saint Charles Borromeo (1538-1584), Cardinal-Archbishop of Milan, the most famous and revered member of the family.