Positioned on the east side of Park Avenue between East 63rd and 64th Streets, 591 Park Avenue offers a rare opportunity to develop within one of Manhattan’s most prestigious corridors. Located in the Lenox Hill section of the Upper East Side, the property sits among historic architecture and cultural landmarks, just steps from Central Park, Madison Avenue’s luxury retail, and world-class institutions like The Frick Collection and The Metropolitan Museum of Art. The site features a 20.42-foot-wide by 97.5-foot-deep lot totaling approximately 1,991 square feet. The existing structure will be delivered vacant, allowing for immediate redevelopment. With R10 and PI zoning and the ability to utilize Universal Affordability Preference (UAP), the site supports a maximum zoning floor area of up to 23,892 square feet. The recent elimination of the Sliver Law under the City of Yes initiative further enhances the development potential, enabling greater height and design flexibility on narrow lots. Architecturally, the site benefits from four-sided exposure, including a north-facing façade adjacent to a church lightwell, which ensures permanent access to natural light and air. This unique condition allows for operable windows on all sides, a rarity in Manhattan, and supports the creation of bright, airy interiors. The property’s boutique scale and prominent Park Avenue frontage make it ideal for a high-end residential or hospitality concept that blends modern luxury with the district’s timeless elegance.