TANZANIA
Kilimanjaro
One of the world's tallest "walkable" mountains, this freestanding 19,340-foot massif draws some 30,000 wide-eyed—and often ill-prepared—hikers annually. Though technical climbing is not required, it's no stroll: A number of those who attempt the five- to nine-day push through rainforest to wind-flayed icefields turn back before reaching the top; about five die en route every year (often from altitude sickness). The payoff for summiters? Views of Africa, in all its brawny magnificence, in every direction. Guides are mandatory; book one in advance through a reputable company, and avoid touts pushing cut-rate outings via the tourist-trampled Marangu Route (the Umbwe Route and others get less traffic). For group treks, seek out experienced companies like Thomson Safaris, which offers hikes on less-traveled trails, with summit-success rates near 95 percent (from $3,990; 800-235-0289, thomsonsafaris.com).

ARIZONA
The Grand Canyon
Few paddling experiences come close to matching the epic 297-mile Colorado River run from Lees Ferry to Lake Mead. There's the monster whitewater (including Lava Falls, called the fastest navigable rapid in North America), the mile-high bisque- and red-hued rock walls, the tent-perfect beaches, and the sheer, walloping Great American West feel of it all. About 22,000 people a year raft a portion of the Colorado's 277 Grand Canyon miles; most travel with one of 16 outfitters licensed by the Park Service, but those with strong river-running skills can arrange a private outing. Good news on that front: As of 2006, noncommercial launch permits are being awarded by lottery (800-959-9164, www.nps.gov/grca), replacing the laughable 25-year waiting list. Motorized or oar-powered rafts are the most common way to go, but purists say nothing beats the grace and responsiveness of a wooden dory. Veteran outfitter OARS offers 15- to 19-day full-canyon dory trips (from $4,535; 800-346-6277, oars.com).

NEPAL
The Annapurna Circuit
After years of violent unrest, a 2006 peace agreement between the government and Maoist rebels promises to return the tourism spotlight to this Himalayan wonder—one of the original adventure travel meccas. No trekking route is more spectacular, or more accessible to reasonably fit hikers, than the three-week, roughly 200-mile inn-to-inn Annapurna Circuit. With a constant backdrop of 20,000-foot peaks, the trail loops from the semitropical city of Pokhara, over 17,769-foot Thorong La pass, on the edge of the arid Tibetan Plateau, and back to the terraced lowlands. Thanks to the détente, U.S.-based outfitters have noticed a surge in interest in Nepal. Wilderness Travel will return to Annapurna this fall after a four-year absence (from $2,795 per person; 800-368-2794, wildernesstravel.com).

FRANCE & SWITZERLAND
The Haute Route
Linking the two most iconic peaks in the western Alps—Mont Blanc, in Chamonix, France, and the Matterhorn, in Zermatt, Switzerland—this famed seven- to ten-day, 70-mile high-country journey is best suited for advanced skiers who feel confident in dicey conditions. (If kick turns on icy steeps aren't in your repertoire, consider waiting for summer and hike the route instead.) Nights are spent in small hotels and dorm-style alpine huts, where you'll find goulash, beer, and the kind of conviviality that generally ends in off-key singing. Even if you're an accomplished ski mountaineer who can parlais français (quick, what does "Danger de mort!" mean?), it's wise to hire a guide (consult chamonix.net) or hook up with an outfitter like Selkirk Mountain Experience ($3,225; 250-837-2381, selkirkexperience.com). Prime ski-touring season is mid-April to mid-May.

ECUADOR
The Galápagos Islands
Straddling the equator 600 miles off the west coast of Ecuador, these far-flung volcanic islands have been the focus of scientists and wildlife lovers since Charles Darwin first scratched his head here in 1835. Now that the Galápagos have become one of the most popular destinations on the planet—120,000 yearly visitors come to spy on the islands' famous giant tortoises, fur seals, and blue-footed boobies—the Galápagos National Park Service keeps tight control on where boat passengers disembark and how long they spend at designated land and underwater visitor sites. The best way to avoid crowds? Charter a private yacht that's stocked with dive gear and sea kayaks. Mountain Travel Sobek can arrange private one- to two-week yacht charters (from $3,795; 888-687-6235, mtsobek.com). Or join Adventure Life's new nine-day hiking trip, with overnights in small inns (from $2,095; 800-344-6118, adventure-life.com).