THERE are 383 aspirational keys in circulation in the Big City, each of them numbered and coded, all of them equipped to unlock any of four wrought-iron gates offering privileged access to undisturbed siestas or tranquil ambulation inside the tree-lined boundaries of Gramercy Park. At age 181, the only truly private park in Manhattan is lovelier and more ornamental than ever; yes, the colorful Calder sculpture swaying blithely in the breeze inside the fence is “Janey Waney,” on indefinite loan from the Calder Foundation.

Alexander Rower, a grandson of Mr. Calder, lives on Gramercy Park, as does Samuel G. White, whose great-grandfather was Stanford White, and who has taken on an advisory role in a major redesign of its landscaping. Both are key-holders who, validated by an impressive heritage, are exerting a significant influence on Gramercy Park’s 21st-century profile. Because Gramercy is fenced, not walled in, the Calder and the rest of the evolving interior scenery are visible in all seasons to passers-by and the legions of dog-walkers who daily patrol the perimeter.

Parkside residents rationalize that their communal front yard is privatized for its own protection. Besides, they, not the city it enhances, have footed its bills for nearly two centuries. Any of the 39 buildings on the park that fails to pay the yearly assessment fee of $7,500 per lot, which grants it two keys — fees and keys multiply accordingly for buildings on multiple lots — will have its key privileges rescinded. The penalty is so painful that it has never had to be applied.

For connection-challenged mortals, though, the park is increasingly problematic to appreciate from within, particularly now that Arthur W. and William Lie Zeckendorf, and Robert A. M. Stern, the architect of their 15 Central Park West project, are recalibrating property values in a stratospheric direction by bringing the neighborhood its first-ever $42 million duplex penthouse, at 18 Gramercy Park South, formerly a Salvation Army residence for single women.