11 Greatest Riverfront Towns

With all due respect to road trips, some of the world's most breathtaking routes aren't fit for four-wheel drives. And they're better off for it. After all, aren't the world's most beautiful views best absorbed at your own pace? These 12 gorgeous trails, paths, and passageways let you do just that—from the saddle of a bicycle, a pair of skis, or your own two feet—without any impatient drivers looming in your rearview mirror. You don't even have to worry about planning the trip—outfitters run road-tested tours through all of these gorgeous spots. SEE THE GORGEOUS SCENERY ALONG THESE TRAILS 1. HIKE INCA TRAIL, PERU  High in the Andes, this 26-mile journey follows in the footsteps of fifteenth-century Incans, leading past a series of ruins to the mystical royal retreat of Machu Picchu. Hundreds of species of exotic flowers (including nearly 200 types of orchids) and tropical birds (giant hummingbirds, tanagers, and Peru's national bird, the bright-red-headed cock-of-the-rock) can be seen along the way. Ancient stone stairs line the path as it leads up through cloud forests and alpine tundra, until the clouds part and the massive Puerta del Sol—Sun Gate—reveals the stunningly preserved granite city of Machu Picchu.Book a Trip: Access to the trail is limited (for preservation purposes), so it's best to reserve your trek well in advance (4-6 months in the high season of May-October). SAS Travel Peru's four-night trek includes bus transport from Cusco, all meals, tent accommodations, and porter service throughout (sastravelperu.com, four-night treks from $610/person). 2. HIKE APPALACHIAN TRAIL, U.S.A.  Cutting through 14 states on the Eastern seaboard, the 2,180-mile "A.T." is one of the longest continuously marked trails in the world, taking in a greater variety of scenery than any other path on the continent. The route starts in Georgia's rugged green Chattahoochee-Oconee National Forest, winds up through the vast valleys and peaks of the Great Smoky Mountains and Shenandoah National Park, then crawls through bucolic New England towns before ending in Maine's incredibly isolated Hundred-Mile Wilderness, one of the most likely spots in the country for moose sightings.Book a Trip: The Appalachian Mountain Club arranges three- and four-day hikes across New Hampshire's White Mountain segment of the trail, a swath of Alpine tundra best experienced when its high-altitude wildflowers are in full bloom (mid-June through September). Trips are led by staff naturalists and include meals, seasonal activities like bird-watching, skiing, or snowshoeing, and accommodation in rustic mountain huts (outdoors.org, three-day hikes from $316). 3. HIKE ZION NARROWS, UTAH  This dramatic gorge cutting through Zion National Park claims a close second place behind the Grand Canyon for sheer, jaw-dropping canyon beauty, yet draws just over half of the more famous park's annual crowds. The path through the gorge—home to some of the world's deepest slot canyons—alternates between gaping, quarter-mile-wide stretches and narrow, 20-foot passageways, and runs directly through the Virgin River's bed—which means hikers who want to go the distance will have to ford waist-deep water from time to time. Still, Zion's fans believe it's worth the wade to stare up between the 2,000-foot-high sandstone walls, lined with lush hanging gardens, streaming with flutes of water, and bouncing with beams of red-orange light.Book a Trip: If you're not the type to wander through canyons on your own—or all that keen on waist-deep wading—the pros at Zion Rock Guides lead beginner-level full-day (dry) hikes that include a stop for lunch and ice cream at the in-park Zion Lodge (zionrockguides.com, from $90). 4. CYCLE HIAWATHA BIKE TRAIL, IDAHO AND MONTANA  The pine-forested Bitterroot Mountains (part of the Northern Rockies) supply the deep-green backdrop for one of the country's most exhilarating rails-to-trails bike-path conversions (completed in 2001). This former stretch of mountain railroad straddling the Idaho-Montana border incorporates 10 covered tunnels (including one, the Taft Tunnel, that's more than a mile and a half long), seven dizzying, canyon-spanning trestles (some as high as 230 feet), and panoramic views across both states. Bonus: The 15-mile gravel trail is mostly flat or slightly downhill, so the smooth ride is doable for most kids and families. (Just be sure that your bike has a headlight for those dark tunnels! It's not only recommended—it's required.)Book a Trip: If you prefer to go it alone, day passes cost $10 through Lookout Pass Ski and Recreation Area (skilookout.com); less-experienced cyclists might opt for a guided tour from Row Adventure Center, which includes a picnic lunch and transportation from Coeur d'Alene, Idaho (rowadventurecenter.com, from $179). 5. HIKE PACIFIC CREST TRAIL, U.S.A.  Consider it the other great American backpacking path: The 2,600-mile Pacific Crest Trail spans the entire West Coast, from the Mexico border to British Columbia. Along the way, hikers pass through 25 national forests and seven national parks, taking in everything from the vivid red Vasquez Rocks near Los Angeles to the deep blue waters and snowcapped peaks of Crater Lake in Oregon. Not to mention Yosemite, Sequoia National Park and the Sierra Nevadas in between. The parallel Sierra Cascades Bicycle Route provides a path for two-wheelers.Book a Trip: Newbies can hook up with the hardcore hikers who are tackling the full trail on Next Adventure's four-day, 32-mile hike along the Oregon Section of the Pacific Crest Trail (nextadventure.net, $400). Guides lead small groups through Mt. Hood National Forest, and all gear, meals, and snacks are included. 6. HIKE TORRES DEL PAINE CIRCUIT, CHILE  This 52-mile trail loops through a section of southern Patagonian wilderness that contains some of the most otherworldly scenery on the planet. Giant blue glaciers and craggy mountain peaks are in abundance here, but the most spectacular formations in this national park are the namesake paines—10,000-foot pillars of granite that spiral up from the glacial-carved valley. The challenging hiking circuit also traverses past green lagoons and expansive ice fields—and if the landscape itself weren't enough, eagle-eyed hikers can spot exotic wildlife (llama-like guanacos, ostrich-esque rheas) roaming the grassy pampas.Book a Trip: Cascada Expediciones offers a five-day, four-night highlights trek; most nights, hikers stay in geodesic eco-domes equipped with sheepskin throws and windowed ceilings for midnight star-gazing (ecocamp.travel, from $1,313). 7. WALK CINQUE TERRE, ITALY  Five colorful villages carved into the cliffs of the Italian Riviera are connected by a series of fifteenth-century footpaths winding directly above the Mediterranean. With autos on these ancient roads still few and far between, this is one of the few places where hikers can still travel car-free through the heart of Old Europe. The scenic vineyards, olive groves and fruit orchards lining the steep cliffs along the trail are bested only by the historic towns themselves, each one filled with centuries-old churches, postcard-perfect homes and high stone walls that cling to the rocks above the sea.Book a Trip: Seven-day treks from UTracks make the central town of Corniglia your base—travelers stay, local-style, in rental apartments—with daily excursions to the surrounding villages and breaks for vineyard tours and swimming (utracks.com, from $860). 8. CROSS-COUNTRY SKI OR HIKE THE KING'S TRAIL, SWEDEN One of Europe's last swaths of genuinely pristine wilderness lies more than 100 miles north of the Arctic Circle. Here, the narrow hiking and skiing path known as the Kungsleden, or King's Trail, is the singular sign of civilization along much of the route. For wintertime skiers the 270-mile route is a snow-swept wonderland; for summer hikers the untouched birch forests come alive with multi-colored flowers blooming under the midnight sun.  Either way, you're likely to encounter herds of wild reindeer—and have  an excellent chance of seeing the Northern Lights.Book a Trip: The eight-day trip led by Nature Travels is rife with extra-special experiences—sauna stops, a boat ride across Lake Ladtjojaure, and the option to add an excursion up 6,906-foot Mt. Kebnekaise, Sweden's highest peak (naturetravels.co.uk, eight-day trips from $1,100). 9. CYCLE ROUTE DES GRANDS CRUS, FRANCE  For folks who take equal pleasure in viticulture and vélo-culture, there's no better bike path than "the road of great wines," a 40-mile route through the heart of Burgundy's famed Côte d'Or (golden slope). The road is lined by a procession of intimate, family-run wineries set along a southeast-facing limestone slope, which is the reason these vines get so much sun (and produce such great wines). The occasional castle punctuates the surrounding landscape. What's more, it's virtually impossible to get lost, thanks to the no-French-necessary road signs stamped with pictures of grapes that are planted all along the route.Book a Trip: The four-night trip offered by Detours in France includes bike rental, luggage transfers, hotel accommodations, breakfasts, two dinners, a wine-tasting meal and private tour of the Gothic Hospices de Beaune, built in 1443 (detours-in-france.com, from $857). 10. HIKE THE WHALE TRAIL, SOUTH AFRICA  If you like long walks on the beach—and we mean really long walks—South Africa's 34-mile Whale Trail is sure to float your boat. The first half, which starts in the Potberg mountains of the De Hoop Nature Reserve, winds east down the verdant green hillsides toward the water; all along the way, trekkers gaze down on the turquoise rock pools and craggy cliff formations that make up this stretch of Indian Ocean coast. Once you hit the ocean, the trail doubles back west, with 17 more miles of secluded, sandy beaches, tide pools, and sea caves. Both segments of the trail have excellent vantage points for the star attraction—abundant southern right whales that populate these waters between June and December. During those months, hikers routinely report seeing 50 or more whales at a time, and some tour operators (like Karoo, below) have a money-back guarantee if you don't spot at least one.Book a Trip: Karoo Tours' six-day hikes include transportation from Cape Town, accommodation in rustic cabins, and all meals (www.karoospirit.co.za, from $555). 11. HIKE MILFORD TRACK, NEW ZEALAND  To many folks—including, presumably, Lord of the Rings director Peter Jackson, who filmed his trilogy there—New Zealand is the ultimate destination for dreamy, fantastic landscapes. The ecologically-diverse Milford Track, which cuts through Fiordland National Park, on the westernmost section of the South Island, is like a sampler platter of the country's most outstanding outdoor offerings. The 35-mile route swings through temperate rainforest, alongside rushing rivers and waterfalls, across wetlands vivid with ferns and moss, and over a narrow alpine pass. But the trail's primary attractions are its magnificent fjords—dramatic, V-shaped valleys carved out of the mountains by glaciers roughly 20,000 years ago.Book a Trip: Guided hikes on the Milford Track don't come cheap: Ultimate Hikes' five-day option includes all meals and snacks, accommodations in cushy lodges, and a cruise on Milford Sound, and starts at $1,488 per person (ultimatehikes.co.nz). If you'd rather strike out on your own, Hike South's self-guided option might fit the bill, with three nights' accommodation in unheated conservation huts for $276 (hikesouth.com). Just be sure to reserve your spot in advance—by several months, if possible—as access to the trail is limited to 90 new hikers per day. 12. MOTORBIKE HO CHI MINH TRAIL, VIETNAM  An elaborate network of mountain and jungle roads built by the North Vietnamese to provide support to troops down south during the Vietnam War, this legendary trail runs the length of the country, winding more than 1,000 miles from Hanoi to Ho Chi Minh City. While segments of the road have since been reclaimed by jungle, the entire route is navigable by motorbike via secluded dirt paths that wind around vertigo-inducing mountain passes where stilted wooden houses are perched on the green mountainsides; through isolated ancient villages; and down to sandy stretches of uninhabited coastline.Book a Trip: Vietnam Adventure Tours has an 18-day, full-trail option, as well as a 3-day, all-inclusive "Taste of Ho Chi Minh" itinerary that offers homestays in Thai stilt houses and in a Muong village (activetravelvietnam.com, 3-day trips from $363). 

When it comes to choosing what airline to fly, the bottom line is often, well, the bottom line: how much it costs to get where you need to go. But with all that laser-sharp focus on saving money, it's easy to lose sight of the little things that can make a trip feel like a journey, rather than an endurance test. To remind you of the ways some companies strive to make life at 30,000 feet a treat—or introduce you to new ones you've never heard about—we present to you our unranked, incomplete, utterly biased list of airlines that haven't forgotten how to delight passengers—with memorable perks like cuddle-class couches, hilarious in-flight announcements, and even in-flight showers. How many have you flown? 1. CUDDLIEST AIRLINE: AIR NEW ZEALAND  While Richard Branson gets a lot of attention for his Virgin Galactic enterprise, Air New Zealand's been making great strides in a different kind of space exploration—one that even those of us without a spare $200,000 can enjoy. In late 2010, the Auckland-based airline unveiled the Economy Skycouch, a padded, fold-out seat extension that allows a pair (or trio) of passengers to stretch out side by side for those longest of long-haul flights—say, between Los Angeles and Auckland. The feature, unsurprisingly, was an instant hit. To get the "cuddle class" experience, travelers need to buy a third seat at half off, typically an extra $500 to $800 for an overnight flight—almost certainly less than the cost of upgrading two coach seats to first class. And while about half the buyers so far have been couples, families traveling with small children have happily been opting for the upgrade, too. Did we say great strides? More like a giant leap—for nap time. 2. FUNNIEST AIRLINE: KULULA AIRLINES  In addition to being South Africa's pioneering low-cost airline—it was the first of its kind to launch there, in 2001—Kulula Airlines, based in Johannesburg, aspires to be the world's funniest airline. Before you even board, there's a sight gag: The bright-green planes are painted with "This Way Up" signs or instructional diagrams pointing out the location of the landing gear, the loo, and the co-captain (labeled, "the other pilot on the PA system"). Then there's the in-flight banter, with gems like, "If you don't like our service, we have six emergency exits," and "Cabin crew is coming down the aisle to make sure that your seat belts are on and your shoes match your outfit." The animated airline's most recent prank? Issuing a press release on April 1 touting their new fleet of Boeing 737-800 seaplanes, which would make water landings near Cape Town, Durban, and Gauteng to reduce congestion on South Africa's runways. In their words, "Kulula has never been scared of navigating unchartered waters, and once launched, we're sure it will go swimmingly." Fortunately, there's no two-drink minimum for this airborne comedy show—and even if there were, it wouldn't cost much. "Drinks with zing," as alcoholic beverages are labeled on the in-flight menu, start under $2 each. 3. MOST IRRESISTIBLE BUDGET-CONSCIOUS AIRLINE: RYANAIR  No one pinches every possible penny as assiduously as Ryanair, the ultra-low-cost Irish carrier. Some of its shameless antics are mythical, though: The airline has never charged for the use of toilets, introduced standing-room-only sections, or sold passengers porn via handheld devices—despite rumors to the contrary. But Ryanair does commit enough acts of random irritation to upset even a Zen Buddhist. The skinflint airline charges a fee of about $10 to charge tickets to an American credit card, a fee to check in either online or at the airport, and a fee of about $16 to sit in an exit row seat. Once onboard, the hassles continue. The seatbacks don't have pockets; the airline instead prints the emergency instructions on the backs of the seats themselves. During a flight, Ryanair crew members constantly hawk snacks, lottery tickets, and smokeless cigarettes. (For a full list of the airline's sins, see ihateryanair.org.) Yet despite it all, Ryanair remains one of Europe's most-flown carriers. Sure, people may love to hate it, but few budget-conscious travelers seem able to resist its siren song of low fares. 4. BEST MAJOR U.S. AIRLINE FOR BAGGAGE HANDLING: DELTA If you've ever thought you were singularly cursed with bad luggage luck, think again: A whopping 42 million bags (on average) are misplaced by airlines worldwide each year. Then, book your next flight on Delta, which had the best baggage-handling record among its peers (that is, the half-dozen largest US airlines) for 2011. Delta had 2.66 reports of mishandled baggage per 1,000 passengers flown last year—an impressive feat, given the airline's complex itineraries. (Budget airline AirTran had a slightly better record, but its simpler route map and lighter schedule give it an unfair advantage; American Eagle, by contrast, doubled Delta's lost-bag reports with 7.32 per 1,000 passengers.) Delta also raised the bar by adding a baggage-tracking tool to its free app for iPhone and Android (as well as to its website, delta.com, for those without smartphones). The app is the first from any airline to allow passengers to enter the number on a bag tag receipt—iPhone users can scan the barcode by snapping a photo of the tag—and watch a bag's journey from departure to arrival, all the way down to its exact claim carousel. If a bag is delayed, the owner can even check the bag's status using a reference number. It's no replacement for a waylaid vacation wardrobe, but it's certainly better than just wondering. 5. BEST (SPLURGE) AIRLINE FOR A MID-FLIGHT SCRUB: EMIRATES  The advent of the superjumbo jet changed the game for aircraft-interior designers, and no one pushed the new boundaries—both in literal and figurative terms—quite like Emirates airlines. Not content to add cushier beds and more elaborate entertainment systems, the Dubai-based carrier was the first in the world to use that additional room on its A380s to install full-height shower stalls for its first-class passengers to freshen up mid-flight. On its Dubai-London route, for instance, Emirates has two snazzy walnut-and-marble "shower spas" to serve its 14 first-class passengers (one person at a time, please). Flight attendants explain the ins and outs in detail before sending folks inside for a scrub—including where to find the oxygen mask, should a change in cabin pressure occur. You'll be happy for the tutorial: When the stall's door is closed, the water turns on automatically—and so does a five-minute timer, complete with a yellow warning light to signal when it's time to rinse off any suds. Even if your financial forecast doesn't call for a "chance of showers," flying coach on Emirates has its own perks: Each seat reclines up to 120 degrees, comes with a power outlet, and has a 10-inch seatback TV screen with 1,200 channels of entertainment. 6. BEST AIRLINE FOR SAFETY DEMONSTRATION VIDEOS [CURRENTLY IN USE]: VIRGIN AMERICA  A nun, a matador, and a bull walk onto on airplane—no, this is not the setup for a joke; it's a list of the characters starring in Virgin America's lighthearted, animated safety-demonstration video. Don't get us wrong—we know that air-travel safety is no laughing matter—but there's a lot to be said for a video that's engaging enough to actually get people to pay attention. (Other airlines have experimented with comic versions of safety videos over the years, but only Virgin America has made it a standard feature.) The video's narrator deadpans all the essential information, inserting an offhand joke here and there ("For the point-zero-zero-zero-one percent of you who have never operated a seat belt before..."), while the animated illustrations showing how, for example, to find and open the compartments where the life vests are stored (in two different spots, depending on your seat) actually do a better job than most. It's the kind of stuff that could save precious seconds in the event of an emergency landing like 2009's Hudson River "miracle"—particularly if everyone on the flight has actually watched the demo. With their eyes open. 7. MOST PUNCTUAL AIRLINE: ALL NIPPON AIRWAYS  Forget the stereotype about German punctuality—Japanese carrier All Nippon Airways (ANA) has set the standard for getting planes to their destinations on schedule. According to a report from FlightStats, the airline landed nine out of 10 flights on time in 2011—the best performance of any international carrier last year—just edging out Japan Airlines International (JAL), the winner for the two previous years. (The industry average was a full 10 percent below ANA's performance, with only about eight out of ten flights hitting their scheduled marks.) ANA operates about 1,000 flights a day, primarily out of its hubs in Tokyo and Osaka, and while the bulk of its routes run within Japan, the airline also flies non-stop daily to Los Angeles, New York, San Francisco, Chicago, Washington D.C., and Honolulu. Seattle and San Jose will be added later this year as the 7th and 8th gateways in the U.S. 8. AIRLINES WITH THE BEST IN-FLIGHT ECONOMY-CLASS MEALS: THAI AIRWAYS AND VIRGIN AMERICA The ultimate proof that an airline's in-flight food soars above the competition? When people choose to eat it outside the confines of the airplane. That's what has happened with Bangkok-based Thai Airways, whose bakery items (curry puffs, fruit tarts, coffee rolls), ready-made sauces, and salad dressings do brisk sales on the ground in its Puff & Pie takeout shops in Bangkok, Phuket and Chiang Mai. Airline passengers have picked it as a winner, too. Last year, the 18 million people who voted in Skytrax's "World Airline Awards" in the economy-class food faceoff overwhelmingly opted for Thai Airways' cuisine, with its focus on local flavors in dishes like massaman curry, stir-fried chicken, and green curry, all served with white rice. (The airline does offer alternatives for fliers with dietary restrictions or less-adventurous palates.)Stateside, our in-flight food is often lacking—not just in style (or appeal), but also in substance. High-fat, low-nutrient snacks have become the order of the day. That's why Dr. Charles Stuart Platkin, a nutrition expert known as the "Diet Detective," set out last year to determine which major North American airlines serve food that's actually worth its weight in calories. His findings showed that Virgin America offers (for purchase) the most nutritionally balanced meals and snacks—like the 370-calorie egg-and-vegetable salad wrap that's packed with hunger-sating protein—of all the U.S.-based airlines he studied. Given that today's fliers are grateful for any food being available at all on planes, we're pleased to see two airlines willing to better their catering games. 9. ECO-FRIENDLIEST AIRLINE: NATURE AIR  You're going to love the windows on Nature Air's planes—and not just because the super-sized panels are roughly four times as large as the ones on the last jet you flew. No, the best part is what you see out of them: the astonishing views of the Costa Rican rainforest, which serve as a constant, vivid-green reminder of just what this regional airline is trying to protect. Of course, flying is never going to be a no-impact form of travel—at least not as we know it now—but Nature Air is wholly committed to reducing its harmful effects. The decade-old airline, the world's first (self-proclaimed) carbon-neutral carrier, invests in carbon offsets for 100% of its emissions via reforestation projects on Costa Rica's Osa Peninsula, and is constantly working toward greater fuel efficiency through better route planning and weight reduction. Over the last three years, they've increased efficiency by seven percent, and their fleet has some of the most fuel-efficient engines flying today. Sounds like as good of a reason as any to plan a spring fling in Central America. 10. TECH-SAVVIEST AIRLINE: SCANDINAVIAN AIRLINES  Imagine checking in for your flight without needing a boarding pass or a barcode, in either print or electronic form. SAS (Scandinavian Airlines) allows just that. Its system at Copenhagen, Oslo, and Stockholm airports, debuting last fall, uses near-field communication (NFC) chips (placed inside stickers affixed to passengers' smartphones) to recognize passengers and their itineraries. Want to check in at an airport kiosk? Simply tap your smartphone, and the kiosk pulls up all relevant information. What about printing luggage tags, passing through security, or boarding the gate ramp to your plane? At each point, just tap your phone, and your info will be zapped to the machines (even if your phone is turned off). As of now, only 50,000 gold-level members of SAS's frequent flier program EuroBonus can use the tap-and-go system when traveling around Scandinavia. This summer, though, manufacturers of Samsung's Android devices—and, possibly, Apple's iPhones—are expected to release new models with NFC chips as a standard perk; here's hoping it's only a matter of time before SAS offers tap-and-go services to all its tech-forward fans. 11. MOST EXPERIENCED AIRLINE: QANTAS  In the movie Rain Man, Tom Cruise says, "All airlines have crashed at one time or another. That doesn't mean that they are not safe." Dustin Hoffman responds: "Qantas. Qantas never crashed." We're happy to report that the claim still holds up—almost. The Australian national airline holds an admirable safety record, having avoided any fatal crashes for more than 60 years. Granted, Qantas has had some lesser accidents in the last few decades, including a crash of a jumbo jet in Bangkok in 1999 that caused injuries (but not deaths), and an emergency landing of a plane in Manila in 2008 after an oxygen bottle exploded. Yet with its very long track record—it's one of the world's oldest continuously operating airlines, founded in 1920—and heavy flight schedule (4,900 flights each week), the "Flying Kangaroo" still deserves kudos for consistency.

From the spectacle of thousands of fireflies flashing in unison in a forest in Papua New Guinea to the wonder of a night sky painted blue, green and purple over a lonely fjord in northern Norway, the planet brims with natural-made miracles.  Pack your sense of adventure, an appreciation for the unpredictable, and follow our lead around the world to spots where light, coral, ice, butterflies—even worms—create some of the world's prettiest drama.  SEE THE PHENOMENA 1. AURORA BOREALIS, NORWAY  When energetic particles from the magnetosphere hit the earth's atmosphere, the skies in the planet's northernmost regions turn into an artist's palette of green and blue swathes and swirls—and, more rarely, red and purple—in the spectacle known as the Northern Lights. The winter of 2012 brought the most intense illuminations in the past 50 years thanks to the Solar Maximum. But the lights make predictable appearances every winter in places like the Lofoten Islands and Tromso, where you can maximize your chances of seeing them during a six-day cruise with Hurtigruten through Norway's northernmost locales. A delivery ship transporting goods and passengers along the coast, the cruise line offers well-priced packages in a notoriously expensive destination (hurtigruten.us, from $1,203 per person for a five-night "Classic Voyage South" cruise from Kirkenes to Bergen, includes full board).   2. MONARCH MIGRATION, VALLE DE BRAVO, MEXICO  The butterfly effect is in full effect every autumn when monarchs from the Rocky Mountains make like snowbirds, flying between 1,200 and 2,800 miles south for the more moderate climes of forested regions high in Mexico's mountains. Guided by the sun's orbit, the butterflies reach Mexico by late October and early November, where they spend the winter hibernating. The trees they converge upon pulse with the movement of their delicate wings. Angangueo in Michoacán is the most popular place to see them. But for less of a tourist crush, head to the high forests two hours outside of Mexico City near the town of Valle de Bravo. See them on your own or book a tour through Tours by Locals (toursbylocals.com, $180 for two people for a tour from Mexico City). 3. CORAL SPAWNING, BONAIRE  Who knew coral had such flamboyant sex lives? Every year—most often in the months of September and October, in the days following the full moon—the coral-clad walls fringing the scuba diving-crazed island of Bonaire become awash with tiny white, orange, and pink spheres (yep, eggs and sperm) that erupt, volcano-like, from the corals and float on the currents to continue the cycle life. In addition to the divers there to ogle the nighttime scene, the reef comes alive with thousands of fishy mouths anticipating an annual feast like no other. Captain Don's Habitat gives you the option to pay one price for accommodations, diving equipment, and guided diving excursions (habitatbonaire.com, $666 per person for 7 nights in an ocean view room; includes 6 single-tank boat dives and unlimited shore diving).  4. FIREFLY TREES, PAPUA NEW GUINEA  Nothing makes you feel like a kid again like chasing fireflies. But it's one thing to see a few flitting in your suburban backyard and quite another entirely to witness several massive trees illuminated with fireflies, like so many strands of Christmas lights strung through their branches. At locations across Southeast Asia—from India and Malaysia to Papua New Guinea—fireflies congregate in trees and bushes along mangrove-lined rivers where they breed, synchronizing their flashes for all to see.  Walindi Resortin Papua New Guinea offers nightly tours to take in the spectacle in the surrounding forest (walindi.com, tours from $8 per person). 5. GEOTHERMAL POOLS, YELLOWSTONE NATIONAL PARK, USA That the planet is broiling with molten rock and unfathomable heat beneath our feet is no secret. Nowhere on earth is that more obvious than in Yellowstone National Park, which contains the world's most diverse display of heat-inspired drama. Old Faithful draws the masses, but a more interesting and varied foray into the geothermal wonders awaits along the boardwalk trail of West Thumb Geyser Basin. The landscape is always in flux, but you can see more than 15 geysers, boiling springs, cones, and deep, scalding pools colored emerald, sapphire, and black pocketing the earth's crust (nps.gov, $25 per vehicle or $12 per person on foot, kids under 16 enter free). 6. JELLYFISH LAKE, PALAU  Swimming in a lake full of jellyfish might sound like a form of medieval torture. But in a freshwater lake of Palau's Rock Islands, the predator-less jellyfish have lost their ability to sting. Sam's Tours runs daily snorkel trips to Jellyfish Lake, reached by a short but steep hike over the limestone island's crest and a quick swim to the other side of the lake. Come sunscreen- and lotion-free so you won't pollute the lake, then gently stroke your way to where the jellyfish are clustering (they follow the sun around the lake throughout the day, soaking up energy). Through your mask or goggles (fins are not allowed), you'll see thousands of the orange-colored polyps pulsing through the green water. Moving amongst them and diving down to feel their soft bodies brush against your own is like something from a dream (Samstours.com, $115 per person for a day tour; park permit is an additional $35 per person). 7. GLOWWORM CABES, WAITOMO, NEW ZEALAND  The limestone caves in the Waitomo region of New Zealand's North Island are home to a fascinating phenomenon—the presence of Arachnocampa luminosa, a unique-to-New Zealand glow worm that manifests itself like an entire galaxy of light on the ceilings and walls of the dark caves here. Boats bring visitors into the dark netherworld of Waitomo Glowworm Cave to see the worms emit light. For more adrenaline, sign up for a blackwater rafting trip to travel deeper into the grottoes via ziplines and tubes (Waitomo.com, from $39 per person to visit the caves, $181 ($163 if you book online) per person for a 5-hour "Black Abyss" blackwater rafting trip).  8. BIOLUMINESCENT BAY, VIEQUES, PUETRO RICO  Imagine the Northern Lights underwater—that's what a boat tour through a bioluminescent bay is like. The brightest such body of water in the world can be found in Mosquito Bay off the coast of Vieques, Puerto Rico. The billions of dinoflagellates (microscopic plankton) that live here give off a blue and green glow when anything agitates the water around them—creating the appearance of swirls of fairy dust as boat engines ply the lake (and swimmers glide across the water). Island Adventures Biobay Tours offers year round trips to Mosquito Bay where you can see the phenomenon for yourself. Set your camera to an ISO of 1200 for the best shot at capturing the scene (Biobay.com, $40 per person). 9. CALVING GLACIER (SERMEQ KUJALLEQ), ILULISSAT ICEFJORD, GREENLAND  The thunder of an iceberg being born is like no sound on earth. Want to see the most active calving glacier in the Northern Hemisphere? Make the trek 155 miles north of the Arctic Circle to Ilulissat, Greenland (you can get there by flying from Copenhagen). Some 20 million tons of ice break away from the Sermeq Kujalleq glacier on a daily basis, bombing into the sea and beginning new lives as drifting icebergs. Ask for a room on the top floor of the Hotel Hvide Falkand you'll be able to watch (and hear!) the groaning ice cap from your balcony (Hotelhvidefalk.gl, doubles from $250). 10. VOLCAN PACAYA, GUATEMALA  You'll likely melt the rubber on your sneakers' soles at some point during the 1.5 hour hike to this active, lava-producing volcano about 15 miles outside of Guatemala City. Consistently active since 1965, Pacaya has erupted more than 20 times in the last 500 years. Be sure to heed local advice on the current safety of hiking Pacaya during your visit. If the volcano is deemed safe for a tour on the day of your visit, enjoy an experience like no other—toasting a marshmallow on a stick over a simmering, bright orange lava flow. Tours can be arranged in the popular tourist town of Antigua, about 90 minutes by shuttle bus from Pacaya (Turansa.com, $15 per person from Antigua).