Aquatic thrills abound in Puerto Rico, from world-class surfing at Rincon where the swells reach 35 feet to relaxed scuba diving, particularly around Mona Island, Desecheo Island and Vieques. On terra firma, the tropical terrain yields prime hiking, horseback riding and rock climbing opportunities.

Take in the lush, volcanically active landscape of Bali while whitewater rafting on the Ayung and Unda rivers. Or get the heart pumping off-shore with an ocean-rafting sightseeing and snorkeling tour in boats that reach 44 miles per hour. Surfers hit the island's western side for big-time swells.

At this behemoth of a canyon, whitewater and calm water rafting trips plunge along 277 river miles, fixed-wing and helicopter tours soar above its mile-deep maw and hikes and mule rides cover the terrain from rim to rim. Horseback tours operate from stables just outside the park's south entrance.

Located about two miles north of the airport, the Kona Coast State Park's trio of tranquil, uncrowded beaches cater to swimming, kayaking, picnicking and snorkeling. It's possible to spot Hawaiian green sea turtles among the arches and caves of the offshore coral reefs. Surfers congregate in the winter for the big surf.

Thailand takes adventure to another level. The south's beaches and islands offer sea kayaking, cave abseiling and climbing on stunning limestone stacks that rise from the Andaman Sea. Jungle treks and canopy tours await inland. In the north, mountains and rain forest backdrop exhilarating outdoor adventures.

Perched in a high mountain valley, Huanglong or Yellow Dragon National Park offers invigorating adventure options. The ambitious can trek to Lhasa, whitewater raft or embark on multi-day river journeys. Alternatively, a five-mile trot brings you to five terraced, temple pools glowing with stunning hues.

Within the nearly 1,200 square miles of one of America's first national parks are top-notch hiking trails to waterfalls, giant sequoia groves, meadows and the iconic granite cliff, Half Dome. Three stables inside the park boundaries lead horse and mule rides that last from two hours up to a full day.

Vietnam's famed jungles are amazingly alive. Jungle trekking reveals a near unimaginable wealth of flora and fauna. Nowhere offers more creature encounters than the country's oldest national park, Cuc Phuong, home to a staggering 43 biodiversity hotspots and over 300 types of rare tropical birds.

The wealth of flora and fauna and opportunities to observe them are unparalleled in the Amazon. Riverboats ply the waters of this fascinating wilderness, home to pink river dolphins, clamorous howler monkeys and raucous toucans. Photograph your adventure, run the rapids or stalk elusive jaguars by night.

The Saharan dune field of Erg Chebbi undulates along the southern Moroccan border, near the small Berber village of Merzouga. Four-wheel-drive and camel safaris traverse this desert region, bringing you front and center with fine red sands piled up to 820 feet high and star-saturated night skies.

This tropical wilderness, home to more than 350 species of birds is a nature lovers' paradise. Explore pristine rainforest where scarlet macaws and toucans swoop and howler monkeys cavort. Horseback ride through dense jungle and along remote beaches where high breaks are perfect for surfing.

Hike the Inca Trail to the majestic Lost Cities of the Incas, hidden in dense Amazonian jungle, 7000 feet above sea level. This ancient road treks 25 miles from Cuzco through deep Andean gullies and is not for the faint-hearted. Climb up to overlook the ruins and the Urubamba Valley from Huayna Pichu Mountain.

With three scenic byways, plus Canyonlands and Arches national parks close at hand, Moab inspires outdoor desert adventures. Cycle, climb or hike among sandstone cliffs and mind-blowing rock formations, raft the Colorado River or take a four-wheel-drive day trip through the arid backcountry.

Cycling through Provence's rolling hills and charming villages, along twisting country roads and past 2000-year-old Roman aqueducts is by turns exhilarating and relaxing. Elsewhere in the region, a slew of activities awaits, from cliff climbing to skydiving to horseback riding or alpine skiing.

Belize's largest island and an often overlooked Caribbean gem offers astounding diving and snorkeling. This English-speaking nation is home to the second-largest coral reef system in the world. If you want to stay atop the waves, this Caribbean idyll provides fabulous fishing, sailing and kayaking.

Dramatic canyons, the world's largest trees and the presence of Mount Whitney, the tallest peak in the lower 48 states, create dream terrain for hiking and backcountry camping. In summer, stalactite-draped Crystal Cave is open for guided tours. In the winter, sledding, skiing and snowshoeing are popular.

A single road accesses the six million acres of wild landscape in Denali National Park, and few private vehicles are allowed to travel it. Instead, park shuttles transport visitors into the wild for backpacking, wildlife spotting and attempts to climb 20,320-foot Mount McKinley, North America's highest peak.

More than 700 miles of trails cut through the forests, alpine meadows and jagged peaks of this national park near the Canadian border. Ranger-led walks, horseback rides and boat cruises explore the park's heritage and geology. In winter, cross-country skiing and snowshoeing routes delve into its wild interior.

Day hikes and camping excursions abound in this Pacific Northwest park, taking in the Hoh Rain Forest, nearly mile-high Hurricane Ridge and oceanfront Rialto Beach. When the snows fall, cross-country and downhill skiing, tubing and snowshoeing cater to outdoor enthusiasts of all ages.

The wealth of wonderful wildlife in the Galapagos defies the imagination. Get up close to fearless sea lions, majestic tortoises and amiable iguanas by hiking, snorkeling, kayaking and diving. Evolve to another level entirely by cycling by cinder cones, lava flows and tunnels or multi-hued beaches.

Set at the ankles of the Andes, the largest ski area in South America also offers thrilling boating, trekking, paragliding and climbing. Lakes abound and the brave at heart can take the plunge into icy Lake Nahuel Huapi which, even in summer, never rises above a chilling average of only 57°F.

Croc-filled rivers, acacia forests and grasslands cover this 200-square-mile reserve in southwestern Kenya, where jeep tours and hot air balloon safaris provide sweeping views. From July to October the wildlife-watching reaches a crescendo as 1.3 million wildebeest migrate into the park, predators in pursuit.

A game drive in search of the Big Five - lions, leopards, cape buffalo, elephants, and rhinos - is only the start in this South African safari mecca. Hit one of four adventure trails in a 4 X 4 for a self-guided tour through the park, take a ranger-led bush walk or soar in a hot-air balloon outside its boundaries.

Set your own pace by cycling through Khmer ruins at Angkor Wat or pedaling the banks of the mighty Mekong. Trek off the beaten path on eco-adventures through the Cardamom Mountains, southern tropical islands or crater lakes of the remote northeast. Add urban adventure and hire a "motodop" taxi in Siem Reap.

Croatia makes quite a splash. With Grade 3 and 4 rafting and kayaking available on rivers that gush through lush forest, and sea kayaking on the coast, it's the perfect place to paddle. For a different pace, dive into the Adriatic's graveyard of vessels, clamber limestone cliffs or sail between 1200 islands.

On the Cooks' capital island, horseback treks, hiking and boat tours provide close-up views of the lush, mountainous terrain. In the surrounding Pacific waters, diving and snorkeling are the top draw: green turtles, reef sharks, moray eels and a cavalcade of tropical fish patrol the islands' coral reefs.

Ever since Lewis and Clark discovered this glacial stream, intrepid travelers have been drawn to the Hood River. The breezes from the Columbia River Gorge, particularly midday, make it an ideal windsurfing and kiteboarding destination and numerous local shops offer lessons for newcomers.

When it comes to mountain climbing, Nepal is the big one, but the home of the world's highest peak has got a lot more to offer than mighty Everest and its neighboring summits. The Himalayan kingdom also offers excitements such as the stunning Annapurna trek, wildlife jungle safaris, rafting and paragliding.

More than a mile wide and averaging 328 feet deep, Victoria Falls is the planet's largest single curtain of falling water and the inspiration for numerous adrenaline-charged activities. Add to the visual rush with bungee jumping, whitewater rafting, helicopter fights, game drives or abseiling.

With 1,400 miles of coral reef stretching along the Queensland coast and 1,500 fish species, the World Heritage List-designated Great Barrier Reef is a scuba lover's dream destination. Accompany underwater exploration with coastal adventures like bungee jumping or rafting through rain forests near Cairns

In the first national park east of the Mississippi River, outdoor activities include climbing pink-granite cliffs, horseback riding or cycling on 45 miles of rustic carriage roads, and fresh water and salt water fishing. The park's 125 miles of hiking trails traverse rugged coastline, forests and mountains.

During the Great Migration, more than a million wildebeest and 200,000 zebras travel across these legendary East African savannas, an area the Masai call "the place where the land moves on forever." Game drives follow the search for sustenance, with most leaving from Arusha or Moshi.

A gulf four times bigger than the Grand Canyon, this chasm in the Sierra Madres offers outstanding backpacking and eco adventures. Even getting to this gorgeous gorge is a thrill: The dramatic 400-mile train trip through almost 100 tunnels and over 37 bridges is one of the world's most stunning.

Ashy plumes of smoke and red-hot lava stream from the active craters in this Big Island park, 30 miles southwest of Hilo. Crater Rim Drive takes cyclists through deserts and rain forests and into the caldera of Kilauea volcano. More than 150 miles of hiking trails cover its 333,000 acres.

Pristine, remote Bhutan teems with turbulent mountain torrents and broad rivers that glide slowly past medieval monasteries, hilltop fortresses and terraced fields. Kayak or raft through this Himalayan wonderland or give your legs the workout and mountain bike through profusions of flowers on ancient mule trails.

Miles of hiking trails cut through the cinder desert landscape around Haleakala, the world's largest dormant volcano. The Maui park is even open around the clock for high-altitude stargazing. Junior ranger programs for adventurous spirits in the 7 to 12 age bracket can be found at the visitor centers.

Hike or mountain bike past castles, lochs, Highland Cows and purple heather in the romantic Scottish Highlands. Experience the beauty of the country as you trot north on the West Highland Way from Glasgow to Fort William or explore the country's first national park, Loch Lomond and the Trossachs.

As one of the wettest places on earth, Milford Sound provides an emerald-green and waterfall-rich backdrop for hiking, biking and kayaking. The Fjordland stretches more than 124 miles south to Preservation Inlet, with an extensive trail network to support travel of the self-propelled variety.

Kota Kinabalu on the island of Borneo is the bustling gateway to acclaimed Kinabalu National Park. The park's high point is 13,400-foot Mount Kinabula, Malaysia's tallest peak, a mecca for climbers. Ninety miles away, thrilling jungle trekking and camping await in the Crocker Range National Park.

The turbulent Futaleufu River thunders a wild course through the heart of Patagonia, its thrashing waters presenting exhilarating whitewater rafting. Hike or trek the backcountry to famed Los Glaciares, take a wildlife safari to penguin colonies or stock up on the essentials and go eco-camping.

Safari on horseback, in a 4 x 4, on foot or by boat to take in Malawi's nine national parks and wildlife reserves, encompassing highlands and marshes. Lake Malawi attracts boaters, fishing enthusiasts, water skiers and snorkelers to its clear, fresh waters that house more than 400 fish species.

The world's largest ski area straddles the French, Swiss and Italian borders. Renowned for skiing, hiking and rock climbing, the area boasts eight natural parks, including Mont Blanc and Gorges de L'Ardeche, and has hosted a hat-trick of Winter Olympics. When snows melts, lavender blooms and olives thrive.

The clock is ticking for the receding snows atop Kilimanjaro, so there's no time like the present to ascend its 19,336 feet. Although it's the highest freestanding mountain in the world, the trekking routes are manageable, traversing from tropics to Arctic. Look for elephants, primates and antelope around its lower reaches.

Stretching from the wooded Dordogne to the towering peaks of the Pyrenees, this vast region is a popular winter sports destination, but one without the hordes that besiege the Alps. Spring's melted snows lure kayakers and rafting enthusiasts. In summer, amateur and advanced hikers take to the hills.

The Out Islands are synonymous with sport, from the depths of the Gulf Stream that yield big game fish to the coral reefs just off shore that are catnip to scuba divers. Sailing, kayaking and beach-combing add action to lazy days in the sun, while resident pink flamingos and rare Bahama parrots color local hikes.

More than 200 miles north of the Arctic Circle waits this land of midnight sun, Northern Lights and spectacular skiing. The Lygen Alps offer a slew of snowy delights, from off-piste skiing and snowmobiling to dog sledding and reindeer trekking. Once snows melt, glacier walks, kayaking and hiking top the bill.

Renowned as the gateway to the glaciers, tiny El Calafate is perched on the brink of Lago Argentino. Take a boat trip to experience ice cracking and glaciers "calving" Los Glaciares National Park. Trot round Lake Roca on horseback. Cast a fly for trout in the shadow of the glaciers in the Rico River.

In the Flinders Ranges, easily reachable from Adelaide, hiking and cycling trails criss-cross the southern region, caves and gorges carve a beautiful swath through the center, and kangaroos bound across red earth in the northern Outback. Four-wheel drive safaris delve into this designated National Landscape.