The Trip Mona Island, 50 miles west of Puerto Rico, is known as the Galápagos of the Caribbean. Mona's carefully protected status (it's home to the endangered giant Mona Island iguana and leatherback sea turtles) guarantees pristine diving.
Why No more than 100 visitors are allowed on the island at any time—score a permit early to camp on Sardinera Beach.
Don't Miss Snorkeling at Playa Carmelita, where visibility can reach 150 feet.
Nekton Cruises, 800/899-6753; www.nektoncruises.com; seven-night trips from $1,820 per person, double. Puerto Rico's Department of Natural Resources (787/724-8774) coordinates permits.
CLASSIC The Trip OARS's five-day kayak tour in Yellowstone and Grand Teton national parks, suitable for beginners and veteran paddlers alike.
Why A support boat provides a restful perch from which to view the majestic peaks. Guides prepare first-class wilderness cuisine at one of the few outfitter camps on Jackson Lake.
Don't Miss A rafting trip down Class I rapids along the seven-mile stretch of the Snake River that connects Yellowstone Lake to Jackson Lake.
OARS, 800/346-6277; www.oars.com; trips run June to mid September; $894 per person.
The Trip Hike the 1,000-foot rock formations of Boynton Canyon at the otherworldly Enchantment Resort in Sedona. The 70-acre desert retreat is surrounded by miles of rugged terrain, including the Coconino National Forest.
Why The two-hour Vortex Walk: acertified Qigong instructor will guide you through the red rocks, among them a majestic spire that locals call Kachina Woman.
Don't Miss The 90-minute Table Thai Massage at the Mii Amo Spa.
Enchantment Resort, 800/826-4180; www.enchantmentresort.com; doubles from $395.
CLASSIC The Trip A 17-day trek along the John Muir Trail—the backbone of California's Sierra Nevada. The Mountain Travel Sobek hike is demanding but spectacular, covering 146 miles of the trail's most scenic section, between Yosemite and Mount Whitney.
Why This is the outfitter's only U.S. multiday trek that provides mules to lug all camp gear.
Don't Miss The predawn climb to watch the sun rise from the top of 14,495-foot Mount Whitney.
Mountain Travel Sobek, 888/687-6235; www.mtsobek.com; $4,400 per person.
The Trip A hike through the Pisgah National Forest.
Why You can choose a one- to three-day Smoky Mountain trek: the company provides camping gear and llamas—smart, agile, calm animals—to haul it. Scale the walls of Panthertown Valley; rock-climbing instructors will meet you there.
Don't Miss Standing on top of 4,629-foot Max Patch Bald for a 360-degree view of the Smokies.
English Mountain Llama Treks, 828/622-9686; www.hikinginthesmokies.com; from $70.
CLASSIC The Trip Canyoneering through Escalante Canyon, in the red-rock country of southern Utah.
Why Thanks to the worst drought in recent history, the surface of Lake Powell has dropped 130 feet, curtailing boat traffic and exposing remote sections of beautiful Glen Canyon and the lower Water Pocket Fold that have been submerged for the past three decades. This year, Escalante Canyon Outfitters plans to lead several five- and six-day trips into these emerging natural wonders. And Abercrombie & Kent offers bespoke trips in the area.
Don't Miss The pictographs and granaries of the extinct Anasazi civilization.
Escalante Canyon Outfitters, 888/326-4453; www.ecohike.com; from $200 a day per person. Abercrombie & Kent, 800/323-7308; www.abercrombiekent.com; four-day trips from $1,345 per person, double.
The Trip The Hayduke Trail.
Why The 812-mile track links up the Southwest's greatest hits, passing through six national parks in Utah and Arizona, including Arches, Zion, and the Grand Canyon. A pair of self-proclaimed desert rats officially opened the trail this spring with the publication of a map-filled guidebook.
Don't Miss The hike in Utah's Grand Staircase-Escalante National Monument, which takes you into several sandstone slot canyons so narrow you can drag your hands along both walls at once.
Deep Desert Adventures, 435/260-1696; www.deepdesert.com; from $800.
The Trip Cabin living above it all at Cedar Creek Treehouse.
Why After a day's hike in the Gifford Pinchot National Forest, you'll stargaze from your bed through the skylights of a wooden cabin50 feet up a 200-year-old rain-forest cedar, or contemplate Mount Rainier from on high.
Don't Miss Crossing the vertiginous Rainbow Bridge to the glass-encased Treehouse Observatory, a smaller lookout 100 feet up a nearby forest giant.
Ashford; 360/569-2991; www.cedarcreektreehouse.com; doubles from $250.
The Trip The Tony Knowles Coastal Trail curls along the Cook Inlet for 11 miles—entirely within the city limits of Anchorage.
Why On clear days, walkers, runners, bikers, and cross-country skiers can view a row of high peaks, including the nation's tallest, Mount McKinley.
Don't Miss Sightings of beluga whales in the inlet.
Anchorage Convention & Visitors Bureau; 907/276-4118; www.dnr.state.ak.us/parks/aktrails.
The Trip High-speed bicycling on the banked oval track at the only international standard velodrome in North America.
Why The track at the Home Depot Center near Los Angeles offers a six-week introductory course in this exclusive sport, often taught by members of the U.S. Olympic Team.
Don't Miss After certification, join the training races: on Saturdays there are endurance disciplines like pursuit, points, and Madison; Sundays are for sprint forms like scratch, Keirin, and match sprints.
Home Depot Center, 18400 Avalon Blvd., Carson; 310/630-2072; www.homedepotcenter.com; course $185.