Karl Lagerfeld arrived just after 8:30 p.m. He pulled up in a black SUV, windows tinted, cutting an inimitable figure in black sunglasses and a black suit, his white hair pulled back in a courtly ponytail. A sea of iPhones hurled into the air as the crowd parted to make way. And, while guests filed into the bottlenecked entrance of Monte Carlo’s Bal de la Rose, Lagerfeld — something of the main event, celebrity-wise, at this annual gala — was whisked away through a side entrance, vanishing as quickly as he had appeared. The iPhones retreated once more.

Amid all his other responsibilities, it’s easy to forget Lagerfeld is also something of a blossoming interior designer. (Stateside, he just nabbed a contract to design the lobby of a Miami real estate development late last year.) The designer directed the look and sound of this year's Bal de la Rose, a blowout dinner party in support of the royal family’s Princess Grace Foundation, and the unofficial kickoff of party season in Monaco since its first incarnation in 1954. Each year, the gala transports the Salle des Étoiles, a grand event space in the city, to another time and place. Past themes have included the art-deco movement and Monte Carlo itself circa 1950; last year, guests were transported to mid-century Havana, Cuba—perhaps not quite the Chanel cruise show, but Lagerfeld, who started designing the Rose Ball several years ago, was clearly having a Cuban moment.

This year, his theme of choice was the Art Nouveau period in Austria, inspired by the Vienna Secession movement and exemplified by the work of Gustav Klimt and Otto Wagner. (Klimt, it seems, is also having a moment: The Austrian artist was among the stated inspirations for the Vivienne Westwood by Andreas Kroenthaler Fall 2017 show.) Graphic prints—reproductions of an ex libris belonging to photographer Emma Bacher—adorned the stage, while the tables were dressed in cloth recalling the carpet of the Belgian palace Stoclet.

By no means did the theme dictate the dress code, though. Monaco’s tropical birds—the European answer to Manhattan's society swans—intent on living out their James Bond fantasies arrived in their very best, showiest gowns. Dancers from the Princess Grace Dance Academy, flanked the entryway clad in matching wigs and Lagerfeld-designed costumes inspired by Klimt’s seminal “Portrait of Mada Primavesi,” handing out raffle numbers and bags filled with Chanel fragrances. Thousands and thousands of dollars worth of couture filed through the opulent space: a man shrouded in a powder-blue Fendi fur stole and glittering Fendi loafers; a woman, her pink-and-red chiffon Valentino cascading over her pregnant belly; Gucci ruffles and Chanel tweed; plumped lips and radiant skin indicating some surgical intervention. The median age: over 50.

“A real bird!” someone murmured as a woman’s wrap molted feathers onto the floor. Fur caps, top hats, and mermaid skirts were de rigueur; a rainbow sherbet sea of colors tumbled through the door. Off to stage left, a table of women in from Istanbul all wore red, or red accents: unintentionally, one woman assured, as her table-mate fanned out a menu that made an unwelcome acquaintance with a lit candle.

Monaco remains a nation of protocol: It’s considered improper for any guest to arrive after the royal family. The international crowd—French, English, and Italian are common languages in Monaco, while Japanese, Chinese, and Arabic could also be heard—milled about for more than an hour before finding their seats, rising in deference to the procession descending from the stage: much of the royal family, including Gucci and Montblanc ambassador Charlotte Casiraghi and her mother Princess Caroline, arm-in-arm with Lagerfeld, as well as the model Daria Strokous. The orchestra swelled, and the royal family took its seat. Waiters were poised in the wings, already prepared to set down the first course. (The menu, too, was a turn-of-the-century-inspired affair, with caviar, chestnuts, and a Viennese charcuterie. Sparkling rosé flowed liberally.)

As dinner came to a close, the Princes Grace dancers emerged onto the stage, accompanying a woman who would lead the raffle. “Je sais que Karl est un excellent danseur,” she assured potential dance partners—"I know Karl is an excellent dancer"—and sure enough, the Chanel and Fendi czar briefly pushed his way to the front of the dance floor with Charlotte, Pierre, and Beatrice Casiraghi in tow, blowing a kiss to one of the musicians on stage. Performers Imany and Hollysiz glided onto the stage in succession, playing short sets as women in slinky lace dresses made a beeline for the dance floor.

Just before 11 p.m., still seated, Lagerfeld himself let loose, taking off his trademark sunglasses. Rest assured, things did not get too crazy—within 10 minutes, the tinted frames were back on.

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