Biblioteca Ambrosiana in Milan, where Jack and I reunited for the final day of our trip, comprises an art gallery, art school and ecclesiastical college, all housed in a rather severe neo-Classical building very close to the Duomo. It was the intention of Cardinal Federico Borromeo, who founded the Ambrosiana in 1609 and named it for the city’s patron saint, that the library, museum and schools be integrated and collaborative. The architecture reflects the cardinal’s aim: From the second-floor galleries, museumgoers can look down at academics working in a nobly proportioned atriumlike reading room.

With a collection of ancient manuscripts rivaling the Vatican’s, the Ambrosian Library is world-class. But nonscholars like me are not deprived of its riches. The library’s ornate 17th-century reading room, the Sala Federiciana, is incorporated into the museum, and, starting in 2009, it has been used to display the institution’s greatest treasure: Leonardo’s Codex Atlanticus, a collection of 1,119 sheets of drawings and captions on subjects ranging from botany to warfare.

Surrounded by the gilded and sepia spines that line this mellow chamber, and dwarfed by its white barrel-vaulted ceiling, I lost myself for half an hour in Leonardo’s inspired doodles of catapults, primordial pontoon bridges and tripod-mounted cannons. The only other artwork in the old reading room is a Caravaggio still life: a basket of slightly worm-eaten fruit stuck with a few pocked, withered leaves. The ingenious improvisations of a restless polymath and this stark memento mori by a disturbed visionary form a perfect pair of bookends for the Italian Renaissance.

Only in Italy, I reflected, and only in a library could I stand, alone and undisturbed, in the center of a great city and peer into the mind of genius.

If You Go

The public rooms of the Biblioteca Nazionale Marciana may be visited using the ticket (19 euros) that provides access to the Museo Correr, Ducal Palace and National Archaeological Museum, all in San Marco Square. Guided tours of the reading room are offered the second Sunday of every month; at other times, guided tours must be reserved by emailing mazzariol@marciana.venezia.sbn.it or phoning 39-04-1240-7238. Information: marciana.venezia.sbn.it.

The Biblioteca Vallicelliana is open to readers aged 16 and older with a valid ID such as a passport. Information: www.vallicelliana.it.

The Biblioteca Ambrosiana is open to readers 16 and older with a valid ID such as a passport. Additional information: bibliotecaangelica.beniculturali.it/index.php?it/1/home.