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illionaire investor and sailor Bill Koch is listing the former Cape Cod estate of philanthropists Paul and Bunny Mellon for $23.85 million, one of the priciest properties currently on the market in Cape Cod. The waterfront compound in Osterville, Massachusetts, sits on 7.5 acres and features a 7,300-square-foot main house with eight bedrooms, two guest cottages, an artist's studio, beach house, and greenhouse.

    The estate was built in 1954 by Paul Mellon, whose family established the National Gallery of Art in Washington, D.C., and was known for his appreciation of fine art and thoroughbred horses. His wife, Bunny, designed the grounds with native plantings, fruit orchards, and formal gardens, creating a horticultural showcase that has been preserved by Koch.

    The property's history runs deep, with the Mellons famously entertaining close friends Jacqueline and John F. Kennedy at the estate. The couple filled the house with fine art, often relocating masterpieces from their primary residence in Virginia each summer. Koch purchased the estate for $19.5 million in 2013 and has used it as overflow for family and guests, renting it out for $25,000 a week.

    Listing agents Joanna Dresser and Kelly Crosby of LandVest of Christie's International Real Estate called the property a rare convergence of provenance and potential, with "a once-in-a-generation opportunity to own a legacy property with both historical provenance and limitless potential."

    Koch is selling because he has acquired an adjacent 10-acre property from the du Pont family and made that his primary Cape residence. He wants to maintain the house as he remembered it, preserving Bunny Mellon's design and legacy.

    The listing comes as Koch continues to scale back his Cape holdings, with plans to sell a nearby 1.75-acre parcel with a 3,700-square-foot house and dock for $10.5 million, and another portion of the former Mellon estate for $16 million. Despite broader market uncertainty, Koch's listing still has a shot at drawing interest from buyers seeking heritage with privacy.