The Ambrosiana Library was founded by the cardinal Federigo Borromeo, who in 1609 opened to the public his private collection of ancient Greeks, Latin, medieval and Oriental codexes. It was called Ambrosiana in honour of St.Ambrogio, patron saint of Milan and it was afterwards enlarged with collections of codes coming both from several religious institutes in Lombardy, as the benedectine monastery of Bobbio, and from private collectors up to 19th century.

The great number and value of codexes, the vastness of the collections make the Ambrosiana one of the most important libraries in the world: especially important are the Arabic and Oriental stocks, the medieval codexes with works by Plautus and Vergilius, the own hand manuscripts by Boccaccio, St.Tommaso of Aquino, Machiavelli, Ariosto, Tasso, Piero della Francesca, Pietro Bembo, Galileo Galilei up to Parini and Beccaria. Precious and rich is the collection of "incunabula" (the first books ever printed in limited and precious editions) and of "princeps" editions (first absolute printing editions of many literature works).

In 1608 a gallery was put beside to the library, with the purpose to support the upcoming Art Academy and to show the correct example to be followed by artists according the directives proposed by the Council of Trento. The academy was actually founded in 1621 and had a flourishing activity for about a century, attracting students and teachers from all around Europe, but it declined during the Enlightment Age, up to the definitive close in 1776, when it was replaced by the new Brera Academy.

But the Ambrosiana Gallery survived to the Academy and nevertheless it enlarged more and more, coming to the current 1500 and more works exposed. Among the most famous paintings, worth to note are the works by Botticelli, Leonardo da Vinci, Raffaello, Luini, Tiziano, Barocci, Brueghel, Caravaggio. There are also some precious collections of drawings, among which the ones by Raphael (with the cartoon of the School of Athens) and the Atlantic Code by Leonardo Da Vinci, with more than 1700 drawings of technical and scientific character.