WALKING INTO BEMELMANS Bar is like stepping through a portal to the past. Located inside the historic Carlyle Hotel in the heart of the Upper East Side, the bar has remained virtually unchanged since the 1940s, when it first opened. It offers a dreamy ascension into an old-school era of decadence and delight, something that’s increasingly difficult to find in Manhattan.

“Bemelmans is a tradition in New York,” says head bartender Luis Serrano, who has worked in various roles at the hotel for 33 years. “Everybody knows it and everybody loves it.”

Over the decades, the legendary hotel has attracted an array of politicians, celebrities, musicians, actors, and socialites. Many presidents, including John F. Kennedy and Ronald Reagan, have slept in its rooms. The Carlyle is where Jackie Kennedy first met Audrey Hepburn, where Kennedy lived with her children in the 10 months after her husband’s assassination, and also the place where her son, John F. Kennedy Jr., ate his last breakfast before the tragic plane crash that took his life. In 2014, Prince William and Kate Middleton chose to stay at the Carlyle during their inaugural trip to New York City, in part, because it was beloved by Princess Diana.

Tucked away on the first floor of the hotel, Bemelmans Bar offers a reprieve from the hustle and bustle of the city outside. It’s a place easy to get lost in, with walls that are covered in whimsical murals depicting animals frolicking around Central Park across four seasons, with the children’s book character Madeline featured among them. That’s because the murals were painted in 1947 by the Austrian-born artist Ludwig Bemelmans, who wrote and illustrated the “Madeline” children’s books, and for whom the bar is named. He received 18 months of free board for himself and his family in exchange for painting the then-new bar, which is the only remaining place where the artist’s work is available to the public.

The final concoction is strained into a chilled martini glass, which is garnished with three green olives. What remains in the shaker is then poured into a glass carafe and served with a trio of snacks (house made crispy cheddar crackers, potato chips, and mixed nuts) alongside the drink — a bonus martini of sorts. “It is a very generous drink,” says Serrano. “People are always surprised.”

One of the few places in Manhattan that still offers live jazzy piano music every night, Bemelmans starts filling up around 5:30 p.m. each evening. And while younger generations are quick to order espresso martinis, Serrano is certain they’ll someday be turned onto the classic rendition the bar is most known for. “Generations of New Yorkers continue to uphold the tradition,” says the seasoned bartender.