“I try not to limit myself to any one style,” says the French designer Florence Lopez, standing in the middle of her first public project, Mon Square, a striking new restaurant on the Left Bank of Paris. “What matters the most in any interior is its personality-it should have a real sense of place, one that is not quite like any other.”

Mon Square is situated in a corner of Paris that is almost achingly beautiful. It is in the heart of the Faubourg Saint-Germain, directly across from the Sainte-Clotilde Basilica, a 19th-century neo-Gothic structure in pale limestone with twin spires. Across the street from the church is a small park, Square Samuel Rousseau, with an oval green lawn and towering chestnuts and plane trees, bordered by a black wrought-iron fence.

            

The restaurant’s owner, 32-year-old Quentin de Fleuriau, is a veteran of the Costes brothers’ empire. He spent more than six years learning the ropes at the Hôtel Costes, had stints at L’Avenue, La Belle Armée, and La Société, and was director of Café Marly. He’d known since he was a teenager, throwing parties at boarding school, that he wanted to have his own spot.

After spending more than two years tracking down the location, he found a faded neighborhood bistro and signed a lease within 30 minutes. “At first, we were just going to redo the banquettes and repaint the walls,” de Fleuriau explains. “But we took everything down and brought in Florence, who has been a friend for many years. She was immediately inspired to make the restaurant feel as though you are dining in the square across the street.”

Lopez was born and raised in Bordeaux, into the Dourthe family, who have produced Médoc wine since 1840. Design was never far away: Her mother was a designer with great flair and the niece of Henri Frugès, who, in 1920, commissioned Le Corbusier to build a modernist neighborhood in Bordeaux, the Cité Frugès, now a UNESCO World Heritage site. At 18, Lopez moved to Paris and befriended such tastemakers as the artists Les Lalanne, the designer Eric Schmitt, the artist and architect Olivier Gagnère, and the sculptor César. She worked for the fabric house Etamine, then headed to New York for an internship at Christie’s and stints with Parish-Hadley and McMillen Inc. Returning to Paris, she worked with Jacques Garcia before striking out on her own.

For more than two decades, Lopez’s atelier has worked out of a walk-up studio on the rue du Dragon, not far from Mon Square, where her clients have included François Pinault, Charlotte Gainsbourg, Daft Punk’s Thomas Bangalter, Carole Bouquet, and Gérard Depardieu.

            

“I had been approached about doing hotels and commercial projects but was never interested until now,” Lopez says of her first foray into restaurant design. “As soon as I visited the site, I had a vision: an imaginary garden, very Parisian, accompanied by the sounds of Claude Debussy, a composer I adore.”

She created four main spaces at Mon Square: a large terrace protected by a long awning; a dramatic central bar; and two dining salons-a pink room to the left of the bar and a green one up some stairs.

                

Elements of nature are everywhere: The front doors have brass handles in the form of branches; the floors and many walls are dark green; and tables have brass bases with tops in green agate or pink quartz.

To complete Mon Square, Lopez called on a trio of artists and artisans. Painter Sacha Floch Poliakoff, the 24-year-old great-granddaughter of Russian-French artist Serge Poliakoff, created murals of bucolic scenes. Bela Silva, a ceramist from Lisbon, made a number of exotic pieces: a flock of colorful birds in brass sconces perched along the outside walls; a massive tree that rises above the bar; and an elaborate mantel in leaves of textured, green-enameled porcelain.

                

A private room off the upstairs dining room is a collaboration with contemporary artist Mathias Kiss. The low-ceilinged space, known as the Ma Kiss Room, has a banana leaf–motif carpet by Madeleine Castaing, a ceiling mosaic depicting nine different skies, and mirrors along all four walls.

Since opening in January, the 150-seat restaurant, which serves seasonal French cuisine, has begun to pull in a lively crowd of film stars, politicians, diplomats, neighborhood regulars, and young and trendy Parisians. “This feels,” de Fleuriau says, “like the beginning of a beautiful story.”