Maurice Tempelsman, the Belgian-born diamond magnate, financier, and political insider who shared a 14-year companionship with Jacqueline Kennedy Onassis after the death of her second husband, Aristotle Onassis, spent the final chapter of his life in a Park Avenue penthouse with nearly 3,600 square feet of wraparound terraces.

Tempelsman, who died at age 95 in 2025—roughly 31 years after Kennedy Onassis—paid $3.3 million for the two-bedroom aerie in 1999, according to records. The Carnegie Hill apartment is now in contract, less than a month after hitting the market for $5.5 million. Allison Bandier Koffman and Juliette Janssens, both with Sotheby’s International Realty, share the listing.

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A staircase ascends from the spacious foyer directly into a window-lined dining room, an unusual arrangement that puts the spotlight on the space’s glossy parquet floors and open views. Nearby, a 24-foot-long living room is anchored by a wood-burning fireplace, while a small staff room or home office with its own bath and a laundry closet is tucked behind the windowed kitchen.

The apartment includes two bedrooms in addition to the staff room. The primary suite features two walk-in closets and a compact private bath, while the guest bedroom—currently fitted as a library with built-in bookshelves—also has its own bath.

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While the interiors have not been significantly updated in recent decades, the apartment has been meticulously maintained, with every principal room opening directly onto the terrace. Landscaped with sculpted trees, flowering plants, and billowing hydrangeas, the outdoor space unfolds as a series of garden-like rooms. Open views stretch south toward the supertalls along Billionaires’ Row and west toward the Central Park Reservoir over the slender white spire of the landmark Brick Presbyterian Church.

Monthly maintenance charges are just over $8,000. Residents enjoy a full-time doorman, fitness center, bicycle and private storage, and other hallmarks of white-glove cooperative living. The 13-story apartment house at 1155 Park Avenue was designed by architect Robert T. Lyons and completed in 1915, adding another layer of pedigree to one of Carnegie Hill’s most established addresses.

Click here for more photos of the Park Avenue home.