How were you to know that in order to enter a Sri Lankan restaurant on a 31st floor-apartment of Hell’s Kitchen building in the 1990s, you had to walk through the porn video store downstairs?

The legend of this “secret” restaurant is just one representation of the restaurants that don’t open their doors to just anyone. With their invite-only rules and under-wraps locations, underground restaurants have long been the rage for culinary elitists and bohemian anti-establishmentarians alike.

But how can the average armchair foodie join the club?

If you want a prime example of an underground restaurant, start by checking out One Pot in Seattle. Its puzzling Web site shows random equations and cryptic messages that suggest a secret code that can only be cracked by in-the-knowers.

The truth is, the roving restaurant, founded by underground restaurateur and author Michael Hebberoy, often has public events.

These culinary experiences take place in a different bar or restaurant each time, and often draw a crowed of taste-makers, chefs, authors, and filmmakers, but you too can join the fray: just email your name to Onepotorg [at] gmail.com and wait for a response (it can take several months).

If that doesn’t work, try another underground Seattle institution, Vagabond, which hosts roaming dinners every Monday night. (Send a message to dinner [at] codenamevagabond.com).

The idea of a secret restaurant is not unique or even new. Cuba has had them for years: Called paladares, many of these dining establishments are actually regulated by government—the rules state that they can only be family-run, serve 12 people at a time, serve “rustic” food, and certain ingredients—like lobster—are prohibited. You might stumble across unregulated paladares, but even the sanctioned ones provide an interesting alternative to state-run restaurants.

Due to the hush-hush nature of these restaurants and locations, they are usually literally off-the-grid. In an avant-garde protest against the Establishment, underground restaurants are usually illegal, unlicensed and unregulated, serving what they want, when they want to … right under the noses of the health department.

With no rules holding them back, these underground establishments often provide fine dining experiences for surprisingly low prices. For example, Ghetto Gourmet, a Bay-area “wandering supperclub” made up of chefs and enthusiastic strangers holds weekly dinner parties at random places, for only about $30 for a four-course meal. If you’re lucky, you may find yourself dining on food created by top chefs such as Alice Waters, executive chef and owner of Chez Panisse, where you would pay up to $125 for a prix fixe menu.

4 Course Vegan in Brooklyn, New York offers $40 full course vegan meals by chefs, giving the lucky eater a unique experience at a price that cannot be beat. The exclusive Shady’s Café in Penland, North Carolina doesn’t even have a price for their menus—you pay what you see fit for your meal.

In some cases, these hidden restaurants offer entertainment along with the food. One of the oldest “secret” spots still running, the eight-year-old Mamasan’s Bistro pays homage to its founder, a DJ/vocalist from Guam, by playing hip-hop beats during its dinner programs—located in the upstairs apartment of a woman known only as Lynette, somewhere in San Francisco’s Mission District.

The good news is that many of these underground dining experiences aren’t so ultra-exclusive anymore. In fact, they’re only a click away. Take Bonsoirée Underground Restaurant, which has an email sign-up list—invitations are sent to a “segment” of the database and recipients need only to RSVP online.

In Melbourne, Australia, the media is abuzz with speculation over something called Zingara Cucina (Italian for “Gypsy Kitchen.”) It started as an underground fine-dining experience in someone’s apartment, and now wanders around nomadically serving communal-style dinners at pay-what-you-want prices. An invitation requires only an email, but dinners can be booked up to a year in advance, so plan accordingly.

And some secrets are just too hard to keep. In Manhattan, a bar called The Back Room was once only for those in-the-know, but word of mouth and the Internet era has made this once-hidden spot a mecca for the hipster set.

Located on Delancey at Norfolk, this “speakeasy” is a throwback to the Prohibition era, and finding it still takes some know-how: It involves navigating a set of creepy steps and walking down a dank ally to uncover the hidden door, which opens up into a surprisingly cozy, elegant room where cocktails are served in tea cups and beer in brown paper bags.

Because really, if it seems forbidden, it’s going to be a lot more fun …

By Michelle Castillo for PeterGreenberg.com.

Looking for more foodie adventures? Don’t miss our Culinary Travel section. You’ll find topics like …

Unexpected Foodie Destinations

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Personal Picks: Gourmet Getaways for Foodies

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Also by Michelle Castillo:

Off-the-Brochure Travel Guide: Edinburgh, Scotland

Things I Wish I’d Known Before Studying Abroad

Things I Wish I’d Known Before Studying Abroad, Part 2

Virgin America: Short-Haul Flights for Hipsters?