With its flickering sign and discreet side entrance, it’s easy to miss CellarDoor. This newcomer to the CBD occupies a sparsely inhabited block of Lafayette Street. But it’s precisely this half-hidden, slightly secretive quality that makes the bar so enticing.

In fact, the three-story brick building, christened the Swoop-Duggins house, has enjoyed a long, alluring history since the mid-19th century, including a tenure as a brothel.

Enter today and you’ll find yourself rewarded with an architectural gem that lures both the eyes and the libido: 14-foot ceilings, exposed brick and beams, jewel-toned walls, wide plank floors and tall windows — exactly the kind of historic space that visitors clamor for and locals take pride in.

CellarDoor has been open about four months. But the bar’s concept is some three years in the making, beginning when owner Gregory Gremillion purchased the building and approached bartender Michael Yusko.

The two conceived of the space together, seeking to offer an intimate spot for quality drinks and food. They wanted to retain the original features and stay true to the building’s sensual history, but also update the space with modern fixtures and colorful, bold art.

As of now, the CellarDoor occupies the building’s bottom floor, and patrons can choose from three different areas: the diminutive six-stool bar, the larger lounge with tables or the side brick patio. It may sound like a lot of space; in fact, each is decidedly cozy and well-suited for catching up with a friend or small group. Yusko says plans are in the works to develop the second floor into an event space within the next year.

A visit to CellarDoor is about more than the allure of exceptional architecture. Yusko, whose previous bartending experience includes Cure and the Bouligny Tavern, has created a cocktail menu ranging from $10-$12 that includes both “classic” and “modern” selections — drinks of Yusko’s own making — in addition to wines by the glass and beer.

There’s a full menu which aside from a burger and cheese plate departs from usual gastro bar fare, and which draws from diverse flavors: Southern, European, Middle Eastern and Filipino.

“I also have a thing for names,” Yusko says, pointing to the “modern” section on the cocktail menu. A quick look reveals a fruity gin and bitters concoction called The Nervous Light of Sunday, Yusko’s first creation as a bartender and named for a chapter of his favorite book, Fred Exley’s classic sports memoir, “A Fan’s Notes.”

There’s also The Drink of Laughter and Forgetting, named after the novel by Milan Kundera, made from green chartreuse and Cynar, a bitter Italian liqueur.

Yusko explains that he tends to avoid overmixing and infusions, preferring to keep his drinks to three, four or five ingredients.

“I like to keep it simple,” Yukso says. If a drink has lasted for decades or even over 100 years, he sees no point in trying to improve it.

And in a city that takes pride in having the oldest or original anything, Yusko is bravely willing to go on record as calling the Old-Fashioned as the oldest American cocktail. However, he generally uses the drink’s original moniker “the Bittered Sling” and claims the drink was concocted in a bar outside Hudson, New York, his own native turf.

As he made a round, Yusko told me that most Old-Fashioneds today are so changed as to be unrecognizable from their original forbearers.

Over the decades, the once stiff and crisp drink (its taste akin to the Sazerac) was altered to become the muddled, overly sweet, cherry-studded version most seen today.

The version Yusko prepares is indeed refreshingly sharp and simple and an elegant departure from usual, candied-up suspects. I was an instant fan.

Good to know: CellarDoor also offers an eclectic dinner menu, with options ranging from small sides like chips and poutine to mid-range main courses, such as mussels and oxtail pot pie. Happy Hour: Tuesday-Friday, 4-6 p.m. $6 “Classic Cocktails” from the menu plus Sazeracs and Pimm’s Cups, wines by the glass, $5 snacks. Brunch on Sundays.

3 more destinations for an authentic old-fashioned

Bouligny Tavern

3641 Magazine St.

Housed in an Italianate shotgun house on Magazine and decorated in a clean-lined mid-century style, this swanky bar offers haute nibbles. A worthwhile Monday-Thursday happy hour menu includes half off fried items.

Cure

4905 Freret St.

This ultra-sleek modern upscale craft bar was one of the first businesses to jump-start the revitalization of Freret Street.

Sylvain

625 Chartres St.

Housed in a mid-century brick building that, like CellarDoor, has retained its original architecture, this Old World eatery and bar offers an understated, chic step back in time.