If you walked along 57th Street anytime in the last few months, you might have found yourself diverted by a tantalizing, but also perplexing sight: In a glass-fronted ground-floor space at 9 W. 57th St., to the west of the building’s entrance and the restaurant Brasserie 81⁄2, is a stunning display of Modern art. Paintings by Balthus, Matisse, Francis Bacon, and Franz Kline share the room with sculptures by Giacometti and Henry Moore. And that’s just what’s visible from the street. What treasures are hidden on the other side of the walls? Chances are you’ll never know. No one is inside. The doors are locked. No dice.

Anyone who lives in New York is familiar with the marketing ploy of the hard-to-get: the restaurant or bar with no sign — maybe even no name — an obscure façade, and a secret phone number. But this is taking things a step further: the museum with no name and NO ENTRY.

A manager at Brasserie 81⁄2 said people ask “all the time” about how they can get into the space. “It’s a private gallery, so we refer them to the building,” he said. “We have no affiliation with the gallery.”

The security staff in the lobby seems alternately amused and fatigued by gallery-related inquiries, which they say they receive constantly. Before a reporter could even get out a question, one guard said: “No, it’s not open to the public — at all!” But he did say the art belongs to the building’s owner.

Although he didn’t name him, the owner is Sheldon Solow. On Forbes’s “World Billionaires 2007” list, Mr. Solow was ranked no. 583, with a net worth of $1.7 billion. He is known to have a substantial art collection, apparently larger than his office or his homes in Greenwich, Conn., East Hampton, and Highland Park, Ill., can accommodate.

“He’s a very serious collector, with a huge range of things, from modern to the best privately held Caravaggio,” a friend of Mr. Solow’s and a proprietor of this newspaper, Michael Steinhardt, said.

Learning more than this, however, proved difficult. Mr. Solow’s spokesman, Michael Gross, described his client as very private. Others have described him as the most litigious person in New York real estate. He has filed as many as 200 lawsuits in state and federal court.

Tenants in the building — which include Bank of America, Chanel, Kohlberg Kravis Roberts & Co., and numerous hedge funds — and friends of Mr. Solow’s declined to comment on the 9 W. 57th St. gallery. A former public official who is said be familiar with Mr. Solow’s collection was “busy until the end of May” and therefore unable to be interviewed, his assistant said. Mr. Gross responded to a detailed list of questions — including how Mr. Solow uses the gallery, whether it would ever be open to the public, and whether, as rumored, the space had recently been rented — with this statement:

“The street-level gallery adds to the selection of great works of art that Mr. Solow has long made available for viewing in the lobby and outside 9 W. 57th St. Mr. Solow believes this art enhances the building’s unique work environment and is a natural extension of the innovative architecture of the building itself.”

How the gallery enhances the work environment when no one can go in is a little puzzling — unless it drives people to work harder so that someday they, too, might have a fabulous collection of art and not let anyone in to look at it. Among a random selection of workers stopped outside the building, some seemed barely to have noticed the art gallery, while others expressed curiosity about why there was never anyone inside.

An employee at Chanel, Cristina Menendez, said she didn’t really pay attention to it. “I usually just come in and out,” she said.

A Bank of America employee who wouldn’t give his name said the gallery was never open and he had only once seen someone inside: the owner. Several hedge fund managers in the building declined to talk about the first-floor gallery, but one, the co-founder of Highbridge Capital Management, Glenn Dubin, conveyed through his assistant a one-sentence response. “How come I’ve never been inside it for a viewing?” Mr. Dubin asked.

The former president and current vice chairman of Chanel, Arie Kopelman, said the art gallery had generated a lot of interest. “Since the exhibition’s been up, I’ve had no less than a dozen people, just seeing me go in the building, ask, ‘What is this?'” Mr. Kopelman said. “They were all asking how they could get in to see it.”

The gallery has a curator, according to another person in Mr. Gross’s office, who said she had spoken to the curator in order to answer a reporter’s questions (though, since the questions were never answered, it wasn’t quite clear why). Inquiries about the curator’s indenty and requests to speak to her were denied.

The explanation behind the gallery’s existence may be very simple: The space is unoccupied, and a great installation of art is more attractive than a “For Rent” sign. But the shroud of secrecy surrounding it frustrates the idly curious as well as appreciators of fine art.
“I always come here, and it’s never open!” a slightly bedraggled man fumed the other day, after pulling on the doors and finding them, as always, locked. “I don’t get it. I don’t understand why they have it here.”