In This Exquisitely Detailed Duplex the Sofa Legs Are Made of Glass and the Closet Doors of Embroidered Cashmere

To design this grand Park Avenue duplex, AD100 designer Julie Hillman assembled an exceptional cast of artisans from around the world, including a British artist known for his three-dimensional works in mirrored glass, a French textile specialist who hand-weaves wall panels, and an Italian sculptor whose functional pieces have otherworldly shapes. The exquisitely detailed results speak for themselves.

“I really love doing things that I haven’t seen before,” says Hillman. “Everything was like a 20-step process. At one point we thought, Why couldn’t we have made this a little easier? But it was, in the end, really, really worthwhile.”

The clients, a New York City couple with three children, implicitly trusted Hillman to reinterpret the classic bones of their 5,600-square-foot apartment and create a sophisticated home tailored to both their social and family life. “From our initial conversation with Julie, it was clear she heard our goals,” says one of the homeowners. “And she has an extraordinary eye.”

Hillman worked alongside Ferguson & Shamamian Architects on the property’s comprehensive yet respectful renovation. One of the bigger alterations happened in the kitchen, where a former laundry room and bathroom were turned into a spacious breakfast corner with a resized window. “We really tried to open up that back space and get more light in,” says Tom McManus, the architect who led the project. “That was really important to the client, who wanted the apartment to feel more fresh.” Overall, however, the original floor plan remained untouched. “It was an excellent layout, very proper, with the bedrooms upstairs and a living room, dining room, and library downstairs, each with a fireplace,” says Hillman.

Her quest to furnish every single room with special pieces began at the private elevator landing, with a custom metal-and-glass front door inspired by sliding doors Hillman had seen at Villa Necchi Campiglio in Milan. The geometric piece, which had to allow light to pass between the vestibule and the apartment beyond but also follow strict safety requirements, was fabricated by Neil Wainland.

Past the entrance, the central gallery’s original marble floors were preserved, creating a dialogue between classic and modern styles. Beneath the gallery’s curved staircase, outfitted with lean new railings, is another geometric form: a 1940s pedestal table by German sculptor Siegfried Pütz. Nearby, an arched black door opens onto a daring powder room with textured black walls, an ebony marble sink, and gilded sconces by Hervé Van Der Straeten.

For the generously proportioned living room, Hillman chose seating of varied shapes so conversations could either flow across the space or stay within intimate pockets. “For me, it’s about having a room where 20 people could sit in, or two people could sit in,” she says. She paired a vintage Swedish wood-framed sofa with an André Arbus daybed with glass feet on one side of the room, anchoring it with a monumental Ingrid Donat bronze coffee table, and on the other side, a series of rounder, more cosseting sofas arranged around a mirrored table by Sam Orlando Miller.

The dining room’s similar amplitude presented a challenge. To avoid having a space that looked “like a conference room,” Hillman commissioned two tables with robust sculptural pedestals from Italian artisan Mauro Mori, which can be pushed together or separated depending on the number of guests (casters hidden beneath their bases allow them to be moved easily). This flexible arrangement called for an oversized chandelier that nearly spanned the room, commissioned from Milanese lighting company 6:AM and composed of clear and matte glass in shades ranging from ochre to smoky gray.

The designer’s emphasis on craftsmanship becomes especially tactile in the library, where Anjou-based textile artist Anne Corbiere wove silvery-bronze metallic thread into fabric panels made for the walls. Her work appears again upstairs in the primary dressing room, this time embroidering cashmere for a series of closet doors, each slightly different from the next.

For Hillman, bringing so many individual voices into one home made the project especially expressive. “I work with these artisans that have a point of view,” she says. “It’s really a collaboration.” The apartment may have strayed far from the easy route, but that seems precisely the point.