In the heart of Milan, the design firm Studio Peregalli has spent the last two years creating one of its most exquisite interiors. The studio—a collaboration between Roberto Peregalli, who is as much philosopher as an interior designer, and the architect Laura Sartori Rimini—was ideally suited to renovate an apartment with such a rich history. These wonderfully layered rooms were originally decorated in the 1950s by Renzo Mongiardino, Studio Peregalli’s own maestro. Both Peregalli and Rimini worked under the tutelage of the legendary Italian decorator until his death in 1998.

After six decades, the rooms were still intact, largely thanks to benign neglect. Unfortunately, there was a bit too much neglect, and the interiors had slipped badly into disrepair. When an Italian couple was looking for a new home, they turned to Studio Peregalli, who remembered the once glorious apartment. The couple bought it on his advice and commissioned his firm to bring back the magic of the Mongiardino interiors. The restoration began with a complete rethinking of the home’s layout to make it more livable for a family with two children.

Studio Peregalli salvaged every single Mongiardino detail that could be saved, from antique wallpapers to the Charles X–inspired bookcases that encircle a library designed in the turquerie style.

The moment one enters the home, one is struck by the impact of the trompe l’oeil decoration that fills the entry hall—the most expressive vestige of Mongiardino’s vision. An imagined landscape framed with trellises, the 18th-century mural once hung in a French château. Studio Peregalli preserved the original, then expanded the pastoral imagery to extend alongside the balustrades that frame the curving staircase. To further embellish the space, some 50 artisans ranging from carpenters to bronzesmiths contributed flourishes with masterful workmanship—from an intricately hand-painted door to a newly laid parquet floor in a geometric pattern of dark walnut and oak.

The trompe l’oeil continues in the master bedroom, where a hand-painted grisaille scenic wallpaper from the 19th century transforms the low-ceilinged space into a whimsical and charming haven.

The deft layering of different styles is a Studio Peregalli trademark. In the living room, the sofa is upholstered in a Turkish rug, draped with a red silk velvet throw, and topped with cushions in a diamond motif (a typical Mongiardino accent).

The effect, especially when set against the backdrop of elaborately decorated walls, is one of controlled exuberance and welcoming luxury. Meanwhile, the sofa—along with others in the apartment—is trimmed with bullion fringe, creating a sense of old-world comfort while adding another allusion to the work of Mongiardino, since he often fringed his upholstery.

The owners have a large collection of European artworks that range from the 17th century through the early 20th. For Studio Peregalli, this required a delicate balancing act in designing spaces that would accommodate such a wide range of subjects and styles.

The end result is interiors that revel in maximalism and sheer variety yet coalesce into a harmonious and unified whole. This celebration of pattern and craft is something of a mission for Studio Peregalli, whose endlessly inventive work is documented in its book, The Grand Tour (Rizzoli), which illustrates a range of the firm’s projects from New York to Tangier.