GRAMERCY PARK, a lush two-acre rectangle at the end of Lexington Avenue, is famously private. And the rules about who can enter its locked gates seem strict enough to keep it that way for a long time.

A TWOFER A rendering of the new condo on Irving Place that is offering buyers a way to get keys to Gramercy Park.
Two keys go to each of the 39 buildings that surround the park. Residents of those buildings can also buy keys, for $350 a year, but only about 400 are in circulation, and they can’t easily be duplicated, according to park officials.
Buyers at 57 Irving Place, a new condominium, are being promised access to the fiercely protected space, too. But what is unusual is that this address is near East 17th Street, a full two and a half blocks south of the park, which starts at East 20th Street.
And, yes, there’s a catch, says Robert Gladstone, the owner of Madison Equities, the Manhattan-based developer: To get inside the park, buyers must first become members of the Players Club.
Co-founded in 1888 by the actor Edwin Booth, the club faces the park and controls a pair of keys.
Acceptance into the club requires a letter of reference from a member, according to John Martello, the Players’ executive director. And if 57 Irving’s residents are accepted, which he fully expects, Mr. Gladstone, a new member, will cover their $1,500 annual dues for five years, he said.
“They’re not going to go back five generations to make sure you’re in the right family,” said Mr. Gladstone, who was married at the club in September.
The 11-story condo, meanwhile, will have nine floor-through units, from three- to five-bedrooms, as well as a three-level 6,800-square-foot maisonette with a garage and saltwater pool.
In every apartment, bathroom floors will be lined with bluestone, and each kitchen will have two wall ovens and two dishwashers.
Although 57 Irving, a $40 million development, awaits state approval, units are expected to be priced from $6.75 million to $18 million, said Mr. Gladstone, who will take a penthouse.
What do the park’s protectors think of the plan to slyly add more people to its gravel paths? They aren’t really fazed, they say, as not everybody who has keys uses them regularly.
For instance, no more than a handful of the Players Club’s 850 members visit the park during a summer week, Mr. Martello said.
Even residents new to the neighborhood, like those at 50 Gramercy Park North, a former hotel site that in 2006 was developed by the Ian Schrager Company into a 16-story 23-unit condo, haven’t measurably increased park use, says Arlene Harrison, president of the Gramercy Park Block Association.
“A lot of people who buy these expensive apartments are foreigners that aren’t necessarily always here,” said Ms. Harrison, who lives at 34 Gramercy Park East, an 1883 co-op.
In fact, the actual number of residents, and by extension park users, may be slightly dwindling, as developers continue to convert multiunit rentals into one- and two-family homes, Ms. Harrison said.
The 1865 red-brick Italianate at 22 Gramercy Park South, for example, once contained eight apartments but is being divided into two condos.
One of them, a triplex penthouse with three bedrooms and five baths, is listed for $11.5 million, says John Burger, a managing director at Brown Harris Stevens, who added that keys to the park may be a draw, but views of it are what really counts.
“It’s really just this little jewel in the heart of Manhattan,” Mr. Burger said. “You’re just not getting views like this anywhere else downtown.”

