June 10 (Bloomberg) -- Architect Philip Johnson hung sparkling curtains of metal mesh in the windows of the Four Seasons restaurant in 1959, then lunched there regularly for decades, keeping an owlish eye on the place through his thick, round glasses. After all, the restaurant is as famous for its modern grandeur as for its food and power-broker patrons.

The Four Seasons is throwing itself a half-century bash tomorrow, with 800 of its closest friends, including Blackstone Group co-founder Peter G. Peterson, home-style doyenne Martha Stewart, and fashion royalty Oscar de la Renta. Then it’s quietly giving itself a facelift.

Through food fads, economic gyrations and a shifting celebrity clientele, the Four Seasons has endured -- but the recession taxes even the legendary adaptability of co-owners Alex von Bidder and Julian Niccolini. These days bass carpaccio is a mere $12 at the bar, and a three-course prix-fixe menu is a steal (in Four Seasons terms) at $59.

With customers’ closed wallets and fickle tastes, pumping cash into this lavish monument to New York’s “Mad Men” era is an act of faith.

“The restaurant has been admirably maintained,” said Belmont Freeman, the restoration architect, “but it needs help.” Though Freeman’s work tends to minimalist surfaces in glass and steel, his role isn’t to transform the restaurant wholesale, but to gently usher the institution into the 21st century, “to reveal more of its elegance,” he said.

The entire interior has been a New York City historic landmark since 1989, permitting little obvious change.

Mies Modernism

Up a bronze-railed stair from a low-ceilinged lobby on East 52nd Street, the 20-foot-high volume of the Grill Room billows grandly upward. It is one of a pair of high, 60-foot-square rooms (or 3,600 square feet each) that the famed International Style architect Mies van der Rohe created at the base of the spare-no-expense Seagram Building, on Park Avenue.

Johnson -- a card-carrying Modernist in thrall to Mies -- leavened the exterior’s austere grandeur in his design for the restaurant with suave, luxe finishes. He covered the Grill Room walls with acres of book-matched French walnut alternating with bronze panels. (The once-golden tones will soon glow anew.)

The main dining room’s iconic marble-lined pool, in which a quartet of tipsy young women once took a naked dip, isn’t going anywhere. Freeman will replace the famous but fading curtains Johnson had made of delicate chains of aluminum anodized in gold, silver and copper. They transform the city outside into an elegantly grainy abstraction and sparkle as they shiver in the air conditioning. He’s found the original Fortuny fabric for the ladies room walls.

‘We Had No Budget’

It is impossible to imagine that kind of lavishness, even with all the showplace restaurants built to the cult of brand- name TV chefs. “We had no budget,” Johnson told architect and historian Robert A.M. Stern. “We just bought things.” They added up to $4.5 million (a staggering $33 million today).

An artisan has already begun cleaning a cloud of bronze rods sculptor Richard Lippold suspended over the bar. A grand stage curtain by Picasso hangs in the passage between the two dining rooms. Mark Rothko was commissioned to create paintings for the balcony over the Pool Room, but realized that the place fed “the richest bastards in New York” and didn’t deliver them. (They are now in major collections.) Jackson Pollock’s “Blue Poles” once hung in a private dining room.

Do changing tastes demand more than a curatorial approach? “How could the Four Seasons be dated?” replied Phyllis Lambert by telephone from the Canadian Centre for Architecture, which she founded in Montreal. “Is Versailles dated?”

Seagram Building

In the 1950s, she persuaded her father, Samuel Bronfman, to hire both Mies and Johnson to design the building named after his spirits empire. She is overseeing the restoration. The work is being undertaken now, she explained, precisely because the Four Seasons is a work of art that deserves proper care.

Noting the vintage look of early lunchers on a recent visit, I asked Freeman if the very idea of the Four Seasons was too tied to legends of yesteryear like Jacqueline Onassis, Henry Kissinger and Barbara Walters. A younger generation gets it, he said. “It’s a modern classic -- like the martini.”

(James S. Russell is Bloomberg’s U.S. architecture critic. The opinions expressed are his own.)

To contact the writer of this column: James S. Russell in New York at jamesrussell@earthlink.net.

Last Updated: June 10, 2009 00:01 EDT