(CNN) — Back in the 1920s, a speakeasy was well-hidden for a reason -- namely to avoid the prying eyes of Prohibition-era police set on smashing stills and emptying bootleg liquor down the drains of New York, Chicago and other U.S. cities.
Ninety years later, some of the world's most renowned bars are similarly hidden away, but only to keep an aura of exclusivity.
Serving classic cocktails, albeit often with a modern twist, they disguise themselves in increasingly ingenious ways so that you truly have to be in the know to get in.
Here are seven of the best:
1. PDT (New York)
As one of the spiritual homes of the speakeasy, New York has to come near the top of any speakeasy list.
No secret bar in the city is as renowned as PDT.
An acronym for Please Don't Tell, this East Village legend is accessed via a phone booth in a hot dog joint called Crif Dogs.
Mixologist Jim Meehan creates brilliant, innovative twists on classics, served to a few drinkers at a time (no standing allowed) kicking back in leather booths and admiring the taxidermy.
PDT recently popped up for a month at Hong Kong's Landmark Mandarin Hotel, to great success.
PDT, 113 St. Marks Place, New York; +1 212 614 0386
2. Bank Bar (Manila, Philippines)
Bank Bar's Nutter Club cocktail.
Manila's burgeoning new Fort district is home to scores of bars and restaurants, none more surprising than Bank Bar.
It may seem like a seriously cheap night out when your date walks you into a 7-Eleven, but there's a surprise in store.
Look for the storeroom -- there are two, many have been caught out -- and walk through, past the provisions to a heavy curtain that pulls aside to reveal Bank Bar.
Inside is a surprisingly large bar with a huge collection of bottles, a buzzing young crowd, cigar room and DJs.
Among the menu highlights is the Nutter Club, made with London dry gin, lemon-pistachio meringue, Angostura bitters and a pistachio salt rim.
Bank Bar, G/F, RCBC Savings Bank Corporate Center, 26th St., Bonifacio Global City, Manila, Philippines; +63 (0)2 544 5776
3. Ounce (Taipei, Taiwan)
In Taipei, Ounce is a cocktail bar hidden away behind a secret door in an unassuming neighborhood cafe.
Opened in 2012, it celebrates all things infused, fermented and distilled.
Don't expect a menu.
Staff speak to every client lucky enough to get in, focusing on delivering a cocktail that fits exactly what they want, be that a classic or an impromptu creation.
4. Lulu White (Paris)
There's a definitive French flavor at Lulu White, visible in the Belle Epoque-style decor in this South Pigalle establishment.
Lulu White is named after an African-American madam who ran a brothel in the historic center of New Orleans in the early 1900s.
There's absolutely no signage in the street, so good luck finding it.
Absinthe is a specialty cocktail ingredient.
5. Foxglove (Hong Kong)
World's best bar to find yourself in during a rain storm.
This new addition to the city's burgeoning bar scene is disguised behind an elegant antique umbrella shop facade, seemingly "Established 1868."
Once you walk through the passageway and press down on a certain umbrella -- there are many to choose from -- you're whisked to a scene straight out of "Mad Men."
Foxglove has a surprisingly large interior, beautifully finished in blue leather and gray marble, designed to resemble first-class airplane cabins and vintage cars.
The Eastern Promise melds exotic ingredients including pepper-infused gin, yuzu marmalade, guava and star anise and a splash of absinthe.
Foxglove, Printing House, 2/F, 6 Duddell St., Hong Kong +85 (0)2 2116 8949
6. Floreria Atlantico (Buenos Aires)
A florist selling wine is just the first layer of trickery disguising this hidden prize in the city's Retiro neighborhood.
Once inside among the bouquets and confused romantics, look for a refrigerator.
It's a door that swings open and leads down to a spacious basement bar decorated with mythical sea monsters on exposed concrete.
Shared plates and inventive handcrafted cocktails are on the menu, but it's the laid back and welcoming atmosphere that turns visitors into regulars, as evenings quickly turn into early mornings.
7. Adults Only (Los Angeles)
This one more than lives up to its name -- the only way to access it is through a doorway in an adult video store in a Sunset Boulevard mall behind a Burger King.
But once through that less than glamorous entrance you're taken straight back to old Hollywood.
Framed vintage movie posters, projected films, a billiards room, exposed brickwork and stained glass all add to the feel, while cocktails include Grounds for Divorce and several named for well known porn terminology.
Adults Only, 7065 Sunset Blvd., Los Angeles; +1 323 469 0040