Arguably one of the most important residences on Fifth Avenue, this exceptionally grand and architecturally important 18-room home is being offered for sale for the first time in over 60 years.It occupies an entire private floor in one of Fifth Avenue's most sought after white glove, limestone-clad cooperatives on the northeast corner of East 63rd Street and Fifth Avenue. The home has 100 feet of frontage facing Central Park, and an impressive enfilade of elegant entertainment rooms spanning over 70 feet along Fifth Avenue. Oversized windows capture beautiful views of Central Park and the Midtown Manhattan skyline.A private elevator landing opens onto an impressive and stately 45-foot gallery with Parquet de Versailles floors and a wood-burning fireplace. The gallery provides access to all of the entertainment rooms of the home. The grand drawing room, formal dining room and inviting library, all have Parquet de Versailles floors, soaring 12-foot ceilings, extraordinary Louis the XV and XVI marble mantles and outstanding Boiseries that were carefully curated from important private homes in Europe.The private bedroom suites are situated in the south wing of the residence, and include five full bedrooms, each with an en-suite bathroom, as well as a south facing study that could easily be converted into a sixth bedroom. The generous master bedroom suite occupies the front south corner of the home, and is flooded with sunlight throughout the day. There are three additional fireplaces in the bedroom wing of the home, one in each of the south-facing bedrooms. Altogether there are six wood burning fireplaces in the apartment.The north wing of the residence offers over 700 square feet of flexible and expansive kitchen space, and an additional adjacent family room for casual dining. Two double staff bedrooms, one full bath and one half bath, complete this wing of the home.In addition, and available for sale separately for $2.5M, there is a guest/staff apartment on the first level of the building. The apartment faces south, east and north. It consists of a living room and three full bedrooms, each having an en-suite bathroom. There is also a fourth bathroom located adjacent to the living room.820 Fifth Avenue is one of Fifth Avenue's most exclusive addresses. It was built and designed in 1916 by Starrett & Van Vleck in the Neo-Italian Renaissance Palazzo style.Residents enjoy the highest level of privacy, service and security. There are also a private laundry room, wine cellar, large storage room and file room located in the basement levels of building. There is a 3 percent flip tax payable by the buyer, and renovations are now permitted throughout the year.