4: Singapore Changi Airport
Sleek, award-winning Changi Airport is one of the world's finest and busiest. If, however, you have a long layover, you might be tempted to leave it. If your transit time is five hours or more, the Singapore Tourism Board offers free two-hour heritage tours of this dynamic city-state, with buses leaving regularly from the arrivals lounge. If you have less time, relax and get back to nature with 40 species of plants in the airport's cactus garden (Terminal 1), giant ferns and graceful fish at the koi pond (Terminal 2), or the tropical butterfly garden (Terminal 3). Super-organized Singapore has efficient signage, and the speedy Skytrain transports you effortlessly between terminals.
5: Istanbul Ataturk Airport
Most passengers arriving at Istanbul's airport need to buy a visa in the local currency before joining the lengthy immigration line. Watch for the signs indicating where to go, and be sure that you have the correct amount at hand to buy the visa — there might not be change available. Note, also, that the airport's dining choices are disappointing and expensive. Before leaving the city for your departure flight, stop in a bakery or shop to pick up snacks.
6: Chhatrapati Shivaji International Airport, Mumbai
The first thing to note is that India's international airport doesn't have the standards you'd expect from a city with such financial clout. Second, dozens of long-haul flights land around midnight, with thousands of passengers catching onward flights a couple of hours later. This means that if you have a layover here, you don't have time to put your feet up right after disembarking. Rather, you must immediately get on one of the lengthy, disorganized lines and have your hand luggage X-rayed yet again before your connection. Wait to relax and get some food after reaching your gate. Finally, at this airport, it helps to be both assertive — especially when it comes to checking flight information and getting updates — and patient. Maintaining a sense of humor helps, too.