NEW YORK • 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 travellers alike), a dining room with food from Michelin-starred restaurants and a bar with more than 120 whiskies. When it is time for your flight, you do not walk to your gate; you are chauffeured - usually in a Porsche or MercedesBenz.

To state the obvious, most airport lounges are not as upscale. Happily, not all are just for first-class travellers. In some, you can get spa treatments and dine on white tablecloths. In others, you are lucky if you score a chair and a banana.

When is it worth the price of admission? Which are the must-see lounges? How do you get in? What is new?

For many travellers, this is intriguing yet unknown territory. At the most basic level, lounges are places to answer e-mail 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, such as the American Airlines' Admirals Club or the United Club. But these are hardly the sole players.

American Express, for example, has the Centurion lounge network: modern airport clubs with pops of colour and locally inspired food and drinks, in cities including 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 set to open in Philadelphia International Airport, and the lounge in Seattle-Tacoma International Airport will be expanded to include additions such as 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 such as Los Angeles and Rio de Janeiro. Travellers with gold status and those flying international business or first class on member airlines (see the Alliance website for details) can also visit any lounge displaying a Star Alliance logo.

There are even lounge networks of lounge networks. The Global Lounge Collection for American Express Centurion and Platinum card members, for example, comprises five programmes with lounges around the world: the Centurion lounge network, Priority Pass Select (with more than 1,000 lounges worldwide), International American Express lounges, Airspace Lounges and Delta Sky Clubs.

HOW DO I GET IN?

With a business or first-class ticket: In general, if you are 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 travellers, paying a few hundred US 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 such as lounge access.

With a day pass: Certain lounges allow travellers to buy this. The Club's is US$40 (S$56.90), though admission is free for Priority Pass, Diners Club International and Lounge Club members. Airspace lounges start at about US$20 a day.

With an annual membership: The cost of a yearly club membership usually depends on your status in the airline's loyalty programme, whether it is a new membership and if it includes your spouse or household. United, for instance, charges its lowest-tier programme members US$550 (or US$1,100 with a spouse).

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

With a friend or relative: If you are on the same flight as someone with an elite status, he may be able to take you into the lounge for free or for a nominal fee.

WHERE ARE THE MUST-SEE ONES? While "must-see" is a matter of personal taste, some lounges tend to be traveller favourites.

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 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 London's Heathrow Terminal 2.

Other popular first-class lounges include Qatar Airways' Al Safwa First lounge at Hamad International Airport; Air France's La Premiere lounge in Paris-Charles de Gaulle Airport; Swiss' First lounge in Zurich Airport; Emirates' lounge in Dubai International Airport; Singapore Airlines' lounge in Changi Airport; and Thai Airways' Royal First lounge and spa in Suvarnabhumi Airport in Bangkok.

MAKE THE MOST OF 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 cannot book in advance, sign up as soon as you arrive.

Dine: If you are visiting an upscale lounge, set aside time for a meal. The British Airways Concorde Room at Heathrow, for example, has private tall booths with waiter service. In Tokyo's Narita Airport, attendants in United's Global First lounge said the sushi they were serving was from popular airport restaurant Sushi Kyotatsu, which Bon Appetit magazine deemed "not just good-for-an-airport good", but also "good-for-Tokyo good".

Nap: Many international lounges have sleep rooms (though most lounges do not make flight announcements, so set an alarm).

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 do not forget to recharge yourself: Grab fruit or a snack for your carry-on.

NYTIMES