A masterpiece of scale, design, and craftsmanship, this extraordinary 22.5-foot-wide mansion is perfectly situated on one of the Upper East Side's most desirable blocks, just off Fifth Avenue and Central Park. Designed by renowned architect Alan Wanzenberg and executed to the highest standards by Steve Mark of SMI Construction Management Inc., the home reflects an impeccable level of detail, marrying timeless elegance with contemporary functionality. The property Is located in a historic landmark district and is protected against vertical expansion.  Comprising five stories plus a finished basement with approximately 8,360 square feet of interior space, the residence is complemented by 1,526 square feet of private outdoor spaces, including a south-facing 660-square-foot garden with an outdoor fireplace and built-in grill, and an 866-square-foot landscaped roof terrace with views of the iconic Manhattan skyline. Inside, the home is defined by high ceilings up to 10'8", abundant natural light, and grand proportions. The spectacular entertaining rooms include a 32-foot-long living room overlooking the beautiful tree-lined street, an elegant formal dining room, a richly appointed library with a wood-burning fireplace, and a custom eat-in kitchen opening onto the garden with a second wood-burning fireplace. The kitchen is outfitted with appliances by Sub-Zero, Viking, and Gaggenau, blending everyday function with chef-level performance. There are five oversized bedroom suites, six luxurious full bathrooms, and four powder rooms. In addition, there is a full ensuite staff bedroom on the garden level. Finishes throughout include solid-core walnut doors and millwork, as well as custom windows by Little Harbor Window, underscoring the residence's level of craftsmanship. A dramatic skylight crowns the top of the home, flooding the grand staircase and interior spaces with natural light, while western side windows further enhance brightness on every floor. All systems have been fully modernized, including an elevator serving the basement to the fifth floor, an eleven-zone central air system, an automatic irrigation system, a Crestron full house system, Lutron lighting and intercom.   A true Manhattan mansion, 4 East 73rd Street presents a rare opportunity to acquire one of the city's most distinguished private residences.