A discreet treasure in one of Cape Cod’s most prestigious enclaves, this exceptional 1.78-acre waterfront estate offers a beautifully preserved five-bedroom residence and a substantial deep-water dock with direct access to Nantucket Sound. Originally part of a historic compound long held by the Mellon family and now by philanthropist William Koch, the property presents a rare chance to own a slice of coastal legacy. Inside, the home features a main-level primary suite with study, stone fireplace, open-concept kitchen, and screened porch opening to an expansive deck with water views—perfect for entertaining or quiet reflection. Guest bedrooms upstairs enjoy generous proportions and stunning vistas. With additional buildable parcels also available, this is a unique opportunity to create a private compound in exclusive Osterville—renowned for its protected waters, world-class golf, and enduring Cape Cod charm.