In line with the construction styles desired by St. Bernard, initially, all frills were banned, and all painted decoration was forbidden inside the abbey. However, in the centuries after the construction of the abbey, considerable changes were made, and Chiaravalle became a precious location for the art history world. Indeed, even today on the counter façade we can admire the main cycles of frescoes in the church (1613-1616), created by Bartolomeo Roverio and brothers Giovanni Battista and Giovanni Mauro della Rovere. The scenes celebrate the history of the Cistercians and are distributed in the main points of the building: the foundation of the abbey, the allegory of the church as a woman, with the Antipope and the Milanese bowing to her, the citizens outside Porta Romana (Roman Gate) offering the model of the church to the saint, a group of artisans busy constructing the building and two miracles performed by the Bourguignon monk during his stay in Milan (curing a child and performing an exorcism). The naves at the sides are free from painted decoration, but host a marble bust of St. Bernard from the 17th century. Two visions experienced by St. Bernard are portrayed on the walls of the presbytery: The Lactation of Saint Bernard and the Dream of Christmas Night, while the vault (1572) features the image of the Four Evangelists and Angels playing Musical Instruments in the rib vaults. The side walls of the choir (1613) feature two frescoes by Luigi Miradori: The Visions of St. Bernard: The Angels respond to the Te Deum and the Angels use golden, silver and black ink to note the fervour of the psalm-singing Cistercians on the left. Going forward towards the dome, there are paintings that decorate the base of the segments, depicting the four Evangelists, and the Doctors of the Latin Church. Sixteen figures of saints are portrayed between the windows of the dome, over the Stories of Our Lady. These works were probably by Stefano Fiorentino, Giotto’s pupil, and can be dated to around the middle of the 14th century. With an extraordinarily sophisticated composition, they depict a single theme: Our Lady’s Transit to Heaven, including the scenes of The Annunciation of the Death of the Virgin by the archangel Gabriel, the deposition of her body in the tomb and the Assumption of the Virgin.
The transept on the right features the family tree of the Cistercian family and on the same wall are the stairs that lead to the only dormitory; above it the Madonna and Child with Angels, masterpiece of the great master of the Renaissance, Bernardino Luini (1512). In the transept on the right we can also admire the Apparition of the Virgin to St. Bernard, the Erection of Cîteaux Abbey, St. Bernard and Angels playing musical instruments and David placating the wrath of Saul. The transept on the left features the following frescoes: Bernard of Poblet killed by a Muslim from Spain whose sister he had converted, St. Thomas Becket, archbishop of Canterbury, assassinated in the cathedral by King Henry II of England’s soldiers, the Coronation of the Virgin, two Cistercian nuns presenting blessed souls to St. Bernard, the Martyr of Cistercian nuns in Poland and the Martyr of the abbot Casimiro and of the monks of Olivia in Prussia.