Nestled on a picturesque tree-lined block in the heart of tranquil Carnegie Hill, 164 East 91st Street is a sun-filled and sophisticated townhouse offering approximately 5,000 square feet of classically laid out interior space across four expansive floors, plus a finished basement. Complementing the interior is approximately 1,600 square feet of private outdoor space, including a glorious tiered garden oasis with a pond, a fourth floor terrace and a partially decked rooftop. This architecturally distinguished residence features oversized picture windows throughout and refined exterior detailing, enhanced by a charming landscaped gated front courtyard and lush window boxes. Grand-scale living is immediately showcased on the parlor level of this home, with soaring ceilings of nearly 13 feet anchored by a wall of glass with twin doors leading to the garden, bathing the floor in warm southern sun and offering a glamorous space in which to entertain at scale. On this floor, the living room is adorned with the first of the houses two handsome wood-burning fireplaces, and in its current open-plan used for dining as well, flows seamlessly into the dining area and the large eat-in kitchen with a built-in banquette affront a wall of windows overlooking leafy 91st Street. The kitchen features extensive storage with beautiful custom cherry wood cabinetry and a full suite of stainless steel appliances. This entertaining level is perfectly completed by a full bathroom as well as two walk-in closets. Above the parlor floor is the first bedroom floor, offering a sprawling primary suite with an oversized primary bedroom and the homes second wood burning fireplace. A dressing room leads to a luxurious five-fixture en-suite bathroom with a spacious double vanity, twin-head stall shower, a deep jetted soaking tub and a dedicated water closet. On this level, there is a second bedroom overlooking the treetops of 91st Street, with a walk-in cedar closet and its own en-suite marble bathroom with a soaking tub. There are two more bedroom suites on the fourth floor, each with excellent closet space and dedicated marble bathrooms with soaking tubs. The bedroom floors are additionally serviced by a laundry closet with a vented washer/dryer. As for the garden level, it is currently being used as an open-plan office with a reception area, built-in desks and cabinetry, a living area, a kitchenette with stainless steel appliances and a recently renovated full marble bathroom with stall shower, all with direct access to the beautiful garden. It can either be retained as is for convenient live/work use, or easily converted to a traditional townhouse garden floor with a grand entrance, kitchen and dining room, or whatever you may choose. The cellar floor below has been fully finished, offering additional living/bedroom space with additional garden access. There is also an oversized renovated bathroom with a stall shower and a huge Jacuzzi bathtub as well as another laundry room and abundant storage.  Also, the current owner is an architect who has drafted plans for the installation of an externally affixed elevator which would not disrupt existing interior space, and already received DOB approval for the addition of a greenhouse on the cellar level and to deck the currently unfinished half of the roof. Unused FAR allows for the addition of approximately 3,000 square feet. Originally built in 1910, 164 East 91st Street is a glorious property in one of the most coveted neighborhoods on the Upper East Side. This 17 foot-wide house has four-zone central air conditioning with smartphone integration, a central vacuum system and a new boiler. A perfect blend of tranquility and convenience, this desirable neighborhood is home to a marvelous array of restaurants and shopping experiences, the finest educational and cultural institutions in Manhattan, and the house is within blocks of Central Park, Museum Mile and all major public transportation including the 4, 5 and 6 trains as well as the Second Avenue Subway. The best of the Upper East Side is at your doorstep.