Mango smoothies beckon. Soft pretzels dangle from a wooden rack. There are platters of Scottish smoked salmon, sausage, bacon, eggs, waffles, pancakes, croissants and cheese beside jars of homemade jams and a honeycomb hive tray.

So begins a Saturday morning in a Lufthansa first-class lounge at Germany’s Frankfurt Airport, where one can while away the hours at the buffet, in a sleeping room or with a hot shower (robes and slippers at the ready). There are private work cabins, a bar, a cigar lounge and a candy station where glass vases brim with gummies, marshmallows and chocolate balls. What could be sweeter, one concludes with Wonka-like wonder, than a first-class lounge?

A first-class terminal.

Lufthansa’s First Class Terminal, also at Frankfurt Airport, is like a lounge on steroids. When you arrive, a valet parks your car. A personal assistant checks you in and accompanies you through security. Inside are amenities found in the airline’s first-class lounges and more, including a bathtub with a rubber duck (coveted by toddlers and business travelers alike), a dining room with food by Michelin-starred chefs and a bar with more than 120 whiskeys. When it’s time for your flight, you don’t walk to your gate; you’re chauffeured — usually in a Porsche or Mercedes.

To state the obvious, most airport lounges are not as upscale. Happily, not all are just for first-class travelers. In some you can get spa treatments and dine on white tablecloths. In others, you’re lucky if you score a chair and a banana. When is it worth the price of admission? What are the must-see lounges? How do you get in? What’s new? For many travelers, this is intriguing yet unknown territory. At the most basic level, lounges are places to answer email or make a call away from the hubbub of the gate. But at their best, lounges are destinations unto themselves.

What is a lounge?

When people think of airport lounges, they usually think of clubs belonging to an individual airline, like the American Airlines Admirals Club or the United Club. But they are hardly the sole players.

American Express, for example, has the Centurion Lounge network: modern airport clubs with pops of color and locally inspired food and drinks, in cities that include Dallas, Houston, Las Vegas, Miami, New York, San Francisco and Seattle. This year, American Express plans to open its first international lounge in Hong Kong International Airport. A Centurion lounge is also coming to Philadelphia International Airport, and the lounge in Seattle-Tacoma International Airport will be expanded to include additions like a private shower suite and a full bar.

Airlines also share lounges. Star Alliance, for instance, has nearly 30 member airlines (United Airlines, Thai Airways and Swiss International Air Lines, among them) and lounges in cities like Los Angeles and Rio de Janeiro. Additionally, travelers with gold status and those flying international business or first class on member airlines (see the Alliance website for complete qualification details) can visit any lounge displaying a Star Alliance logo.

And then there are independent lounges for travelers on any airline, traveling in any class. The Club, for one, is a chain of day-pass lounges in Dallas/Fort Worth International Airport, Orlando International Airport, Boston Logan International Airport and other airports. Airspace Lounge is another day-pass brand, available in cities like Cleveland, New York and San Diego. Also, the USO has lounges in some airports for military members and their families.

There are even lounge networks of lounge networks. The Global Lounge Collection for American Express Centurion and Platinum card members, for example, comprises five programs with lounges around the world: the Centurion lounge network, Priority Pass Select lounges (more on this below), International American Express lounges, Airspace Lounges and Delta Sky Clubs.

Some hotels have airport lounges. The Four Seasons Resort Lanai recently opened a pale wood and cream lounge with food, drinks, Wi-Fi and iPads for guests of the resort in Honolulu International Airport. Lanai “ambassadors” help guests check in, book activities and vehicle rentals, and make restaurant reservations before they travel on to the hotel (they can also use the lounge on the way back).

As if that weren’t enough, there are more specific types of lounges, such as arrivals and departures lounges, or first class and business class lounges, though the same lounge may be used for both. Check your airline website to see which you can use.

Even the most basic domestic lounge can make travel easier. You can grab a snack, coffee, a magazine. You can charge your laptop and use Wi-Fi; the desk staff can help you change seats or flights. In the best (usually international) lounges you can shower after a long flight, eat dinner and unwind with a cocktail or free spa treatment.

How do I get in?

With a business or first class ticket: In general, if you’re flying international business or first class on a major carrier, your boarding pass will get you into that airline’s lounge. In certain cases, you can use the lounge of an airline in the same alliance, but be sure to read the rules. Star Alliance members, for instance, are not allowed to use Lufthansa’s first-class lounges or the first-class terminal in Frankfurt.

With a credit card: For frequent travelers, paying a few hundred dollars a year for a Visa or American Express card may be well worth it, not only for the award points, but also for perks like lounge access. Consider the Chase Sapphire Reserve card. A relative newcomer, it costs $450 a year, though some of that comes back to you: As you spend on travel-related things like taxis and hotel rooms, you’ll see those costs deducted from your card bill, up to $300 a year. The card has other perks as well, including membership in Priority Pass Select, which has more than 1,000 lounges worldwide. Of course, you could just buy an annual Priority Pass membership, but the fee is at least $99, plus $27 each time you visit (bringing a guest is another $27), and you wouldn’t get the additional benefits of the Chase card.

Co-branded airline credit cards may include lounge access (like the $450 Citi/AAdvantage Executive World Elite MasterCard, which comes with an American Airlines Admirals Club membership). Another option is American Express Platinum. It’s $450 a year and has myriad perks, including access to the Global Lounge Collection.

With a day pass: Certain lounges allow travelers to buy these. The Club is $40 (though admission is free for Priority Pass, Diners Club International and Lounge Club members). Airspace lounges start at about $20 a day. If you’re an American Express credit or charge card holder, you can purchase a day pass for a Centurion Lounge ($50). You may also buy day passes for airline-branded clubs. Virgin America lounges and clubhouses are about $30 to $75 for adults without status. American, Delta and United charge $59 in select locations (though when a lounge is busy, it may not accept day passes).

With an Annual Membership: The cost of a yearly club membership usually depends on your status in the airline’s loyalty program, whether it’s a new membership and if it includes your spouse or household. United, for instance, charges its lowest tier program members $550 (or $1,100 with a spouse). Membership for Premier 1K members is $450 (or $1,000 with a spouse). You may be better off paying for a travel credit card like Platinum from American Express: It costs the same or less (and there’s a $200 airline fee credit for incidentals like checked bags and in-flight food), and it gives you a number of benefits, including $100 credit for the cost of Global Entry — the U.S. Customs and Border Protection program — and access to more than one lounge brand.

With miles: You can use airline miles to buy an annual membership. For example, Delta charges $495 or 47,000 miles for an individual membership (guests are $29 each per visit). Generally speaking, this is not a good use of your miles; save them for travel.

With a friend or relative: If you’re on the same flight as someone with elite status, they may be able to bring you into the lounge for free or for a nominal fee. (The number of family members or companions allowed varies from lounge to lounge.)

Where are the 
must-see ones?

While “must-see” is a matter of personal taste, some lounges tend to be traveler favorites. Skytrax, an industry consultancy, said more than 18 million fliers participated in the Skytrax World Airline Awards last year and awarded Best First Class Lounge to Cathay Pacific in Hong Kong. The Best Business Class Lounge award went to the Qatar Airways Al Mourjan Business Class lounge at Hamad International Airport in Qatar. Plaza Premium Lounge won Best Independent Airport Lounge for its club in Heathrow Terminal 2.

Other popular first-class lounges include Lufthansa’s First Class Terminal in Frankfurt; Qatar Airways’ Al Safwa First lounge at Hamad International Airport; Air France’s La Première lounge in Paris Charles de Gaulle Airport; Swiss’ First lounge in Zurich Airport; Emirates’ lounge in Dubai International Airport; Singapore Airlines’ lounge in Singapore Changi Airport; and Thai Airways’ Royal First lounge and spa in Suvarnabhumi Airport in Bangkok, to name but a few.

I once stepped off a plane and was instantly whisked through Suvarnabhumi Airport in a buggy and escorted through security to the Thai Airways Royal First lounge, where my party was asked if we wanted massages before a flight to Indonesia. (I did.) We were then led to a couch with colorful silk pillows in a private living room of sorts, replete with leather armchairs, coffee table, large television, desk and computer. A woman brought menus and took a drink order. Then it was off to the Royal Orchid Spa across the hall for a vigorous neck and shoulder massage.

Good as these may be, new lounges are always popping up. Among them is United’s Polaris lounge in Chicago O’Hare (for customers traveling United Polaris first or business class on long-haul international flights, as well as Star Alliance first and business class travelers departing on international flights), which has table service, showers and daybeds.

At Abu Dhabi International Airport in the United Arab Emirates, Etihad Airways opened its First Class Lounge and Spa with a bar, gym, cigar lounge, spa, barber, nail bar, playroom, prayer room, relaxation room (in which leather chairs are bathed with soothing sounds and images on a video wall) and menus with Arabian, Indian and other international cuisines. For the youngest travelers, there is a nanny from Norland College, a child-care training school in Britain whose graduates appear to be good enough for the Duke and Duchess of Cambridge.

Make the most 
of the amenities

Spa: Free spa appointments go fast. Find out if the lounge allows you to book in advance (and if the treatments are free; some lounges charge). If you can’t book in advance, sign up as soon as you arrive.

Dine: If you’re visiting an upscale lounge, give yourself enough time for a meal. The British Airways Concorde Room at London Heathrow, for example, has private tall booths with waiter service (don’t feel you have to put on airs; I had a cheeseburger and Champagne). In Tokyo’s Narita Airport, attendants in United’s Global First lounge said the sushi they were serving was from the popular airport restaurant Sushi Kyotatsu, which Bon Appétit deemed “not just good-for-an-airport good,” but “good-for-Tokyo good.”

Nap: Many international lounges have sleep rooms (though most lounges don’t make flight announcements, so set an alarm). Afterward, you can shower or relax in a bath.

Work: If you like to arrive at the airport early, a lounge is an ideal place to avail yourself of free Wi-Fi and printers.

Play: Some lounges have play spaces with activities and television, so kids can be kids.

Refuel: Charge your phone, tablet and laptop. And don’t forget to recharge yourself: Grab fruit or a snack for your carry-on.