Certosa is the Italian translation of Charterhouse: a monastery of the cloistered monastic order of Carthusians founded by St. Bruno in 1044 at Grande Chartreuse.

Gian Galeazzo Visconti, hereditary lord and first Duke of Milan, commissioned the building of the Certosa from the architect Marco Solari, laying the foundation stone on 27 August 1396, as recorded by a bas-relief on the facade.

For the Duke, the Duomo became the church for burial of nobles, patricians, people, artisan and merchant guilds of Milan, while the Certosa would service the Duchy.

The Carthusians enjoyed substantial income from the vast agricultural lands donated by Gian Galeazzo Visconti and his successors the Sforza.

The traffic of Carrara marble towards the Certosa was so voluminous that the Carthusians themselves came to resell it to other Lombard shipyards and in particular to the Veneranda Fabbrica del Duomo di Milano.

The construction contract obliged the monks to use part of the revenue of the lands held in benefice to the monastery to continue to improve the edifice.

The Certosa initially only held 12 Carthusian monks, who lived in total cloistered life, and bound by a contract that provided for the use of part of their proceeds (fields, land, income, etc.)

In the eighteenth century the monastery was the owner of large estates (in part already donated by Gian Galeazzo and his successors) scattered in the fertile countryside between Pavia and Milan, such as Badile, Battuda, Bernate, Binasco, Boffalora, Borgarello, Carpiano (it was the property of the monks also the castle of Carpiano and the church of San Martino), Carpignano, Milan, Giovenzano, Graffignana, Landriano, Magenta, Marcignago, Opera, Pairana, Pasturago, Quintosole, San Colombano (where they also controlled the castle of San Colombano) Torre del Mangano, Trezzano, Velezzo, Vidigulfo, Vigano Certosino, Vigentino, Villamaggiore, Villanterio, Villareggio and Zeccone, which added up to 2,325 hectares (5,745 acres)of irrigated land.

In the faded entrance lunette, two angels hold the coat of arms of the client Gian Galeazzo, with the Visconti snake and the imperial eagle.

The sober form of the roughly finished brick front can be seen in a fresco by Ambrogio Bergognone in the apse of the right transept, painted in 1492–1495,[16] when work was commencing on the new facade, portraying Gian Galeazzo Visconti offering the model of the Certosa to the Blessed Virgin.

Its profile, with roofs on three levels, has been compared to the churches of Santa Maria del Carmine in Pavia and San Petronio in Bologna;[17] among the architects in close correspondence at all three projects, Borlini ascribes the form of the original facade at the Certosa to Giacomo da Campione, who was working at Pavia while his uncle Matteo was completing San Giovanni in Monza.

[21] The frescoes that adorn the walls and vaults of the transept are due, as has been said, to Ambrogio Bergognone assisted by a group of unknown masters, including the very young Bernardo Zenale.

In place of the two tables scattered on either side of the Eternal Father, the two panels with the Doctors of the Church by Bergognone were inserted at the top, made for another Altarpiece of the Certosa which was subsequently dismembered.

An Annunciation has disappeared; three panels, the Virgin Adoring the Infant Christ, St. Michael and St. Raphael with Tobias are on display at the National Gallery of London, in the United Kingdom.

In the southern transept is the tomb of Gian Galeazzo Visconti, begun in 1494–1497 by Giovanni Cristoforo Romano and Benedetto Briosco, but completed only in 1562.

The sculptures on the tomb were carried here in 1564 from the Milanese church of Santa Maria delle Grazie, the statues generally being considered the masterwork of Cristoforo Solari.

The altarpiece with Mary Magdalene at Christ's feet is by Giuseppe Peroni from Parma (1757), while the fresco decoration is by Federico Bianchi, a pupil of Ercole Procaccini (1663).

[27] The fourth chapel, whose altar is equipped with alabaster columns, preserves a frontal with the Massacre of the Innocents, by Dionigi Bussola from 1677, while the altarpiece by the Cremonese painter Pietro Martire Neri (1640–41) depicts the Adoration of the Magi .

[30] The seventh chapel on the left preserves an altarpiece depicting the Virgin of the Rosary, a masterpiece by the Milanese Baroque master Pier Francesco Mazzucchelli, painter in the service of Cardinal Federico Borromeo, who creates a work of refined elegance in delicate tones, in the elongated shapes and in the sweet expressions of the characters.

It is a composite cycle, with scenes drawn from the New Testament, hagiographies of Carthusian and other saints, skilfully inserted into Gothic architecture through a complex system of decorative squares, framing large sacred scenes and smaller panels with isolated figures of evangelists, doctors of the Church, prophets, sibyls, Carthusians and blessed saints.

The Certosa possesses an important collection of stained glass windows, executed to cartoons by masters active in Lombardy in the 15th century, including Zanetto Bugatto, Vincenzo Foppa, Bergognone and Hans Witz.In the presbytery there is the large Renaissance carved wooden choir, commissioned by Ludovico il Moro.

In the median cusp, inside a tondo supported by angels, the figure of God dominates, while the base of the triptych presents a piety, flanked by 14 aedicules with as many statuettes of saints.

The single large rectangular room was frescoed in 1600 by the Sienese painter Pietro Sorri, who, inspired by Michelangelo's Sistine Chapel, covered the great vault with biblical episodes, monumental figures of prophets in niches, and graceful cherubs revolving in goblets.

[39] An elegant portal, with sculptures by the Mantegazza brothers and Giovanni Antonio Amadeo, leads from the church to the Small Cloister (in Italian: Chiostro Piccolo.)

The arcades have columns with precious decorations in terracotta, with tondoes portraying saints, prophets and angels, alternatively in white and pink Verona marble.

On the west wall of the hall is a small fresco, the oldest in the monastery, in the late Gothic style depicting a Madonna and Child by Zavattari.

The lowered vault has the oldest decoration, including a Madonna and Child and Prophets in Spectacles attributed to Ambrogio da Fossano, while in the center is the sun or radiant ray, emblem of the Visconti dynasty.

The building, modified in 1625 by an intervention on the facade by the architect Francesco Maria Richini, has a linear succession of windows between semi-columns that give brightness to the entire structure.

In the years from 2002 to 2006, most of these casts were restored and placed, with a new layout by the Superintendence for Architectural and Landscape Heritage of Lombardy, in the ground floor gallery of the Ducal Palace.

Then there is the study, frescoed in the second half of the 16th century with a trompe-l'oeil landscape, punctuated in squares by monumental monochrome figures with serpentine legs, called telamons, while the vault, decorated with spectacular grotesques painted with a brush tip.