Skiing in Banff National Park, Alberta
Banff National Park is Canada's oldest and most famous national park. From its humble beginnings as a 16-mile hot springs reserve, Banff National Park now consists of 2,564-square-miles of snow-capped peaks, glistening glaciers, and sweeping vistas, nestled in the heart of the magnificent Canadian Rockies, which boasts superb cross-country skiing and world-class downhill skiing.

Hiking and Paddling Big Cypress National Preserve, FL
Winter in these parts is more accurately referred to as "the dry season." And it's by far the best time to visit the preserve. Falling water levels within Big Cypress draw wildlife to concentrated ponds and canals, providing excellent viewing opportunities. This season also offers hikers and boaters relief from the heat and mosquitoes that characterize much of the rest of the year. Hikers can get a real taste of the 1,400-mile Florida Trail, 45 miles of which runs through Big Cypress. The preserve also offers a greater number of ranger-led activities during "the dry" that provide an in-depth look into the area's natural and cultural resources.

Skiing in Grand Mesa National Forest, CO
The Grand Mesa National Forest lies in the heart of U.S. alpine country alongside Uncompahgre and Gunnison national forests. It's a land of 14,000-foot peaks, fast-flowing creeks, alpine lakes, deep spruce forests, red-rock gorges, and lots of black bears. The forest is spectacular year-round, with mid-summer alpine meadows painted by wildflowers and autumn displays of brilliant gold aspen trees. But winter is when this stretch of the Rockies really shines, especially at the Powderhorn Ski Resort, which gets an average of 250 inches of the white stuff each winter, hence the name. The forest also boasts hundreds of miles of cross-country skiing and snowshoeing trails.

Water Sports and Hiking in Virgin Islands National Park, USVI
Virgin Islands National Park's diverse beaches, coral reefs, historic ruins, and hiking trails provide endless exploration opportunities. Go hiking, bird watching, and camping to unlock the islands' secrets. Rock carvings from the Taino people are scattered throughout the park, particularly on the Reef Bay hiking trail. Head offshore for scuba diving, sailing, kayaking, or windsurfing in the crystal-blue waters. This park has it all—including a refreshingly warm climate in the middle of an otherwise frigid winter.

Ozark-St. Francis National Forests, AR
Arkansas' northwestern corner is composed of lush green plateaus, interspersed with occasional faults and cracks, and the erosional scars of swift-flowing rivers. Here, in the Ozarks, the Boston Mountains present sheer-sided slopes and vertical bluffs of sandstone. And the mighty Mississippi displays its grandeur in the St. Francis unit of the forest more than in any other forest in the United States. Hop on the Ozark Highlands Trail, which remains relatively undiscovered, and catch winter views of unique ice formations and sweeping forest vistas.

Snowshoeing and Skiing in Great Basin National Park, NV
From desert basins to glaciers tenaciously clinging to the flanks of 13,063-foot Wheeler Peak, Great Basin serves up a rich variety of backdrops for hikers, mountain bikers, anglers, and wildlife lovers. In winter, the park continues to bustle with skiers and snowshoers. Novice skiers can find gentle slopes, and experienced ski mountaineers can tackle steep and deep backcountry runs. Snowshoeing and cross-country skiing trails abound.

Hawaii Volcanoes National Park, HI
Peer into the glowing cauldron of an active volcano, then summit a 13,000-foot mountain, and later, catwalk atop cliffs that plunge into an impossibly blue sea. It's all in a day's work—or rather, play—at Hawaii Volcanoes National Park on the Big Island. Hawaii Volcanoes encompasses more than 200,000 acres of astoundingly diverse terrain. The altitude in the park ranges from sea level to the summit of the earth's most massive volcano, 13,677-foot Mauna Loa. Arid deserts exist within a few miles of lush forests. And both beckon those with an adventurous spirit.

Carlsbad Caverns National Park, NM
The 47,000-acre Carlsbad Caverns National Park was designated a World Heritage site in 1995, a landscape considered of “outstanding universal value with exceptional geological features.” The caves themselves lie in the Guadalupe Mountains—a Permian-age fossil reef—and contain one of the world's largest underground chambers.

Camping and Snow Sports in Kettle Moraine State Forest, WI
The snowy season has become a popular and busy time in the Kettle Moraine State Forest. The Southern Unit includes some 30 miles of groomed and marked cross-country ski trails, and the Emma Carlin Trail is set aside for winter hikers and snowshoers. Campsites are open during winter at Ottawa Lake. An enclosed picnic shelter is available for gatherings, and there are three great ice fishing spots. Just 85 miles north of the Southern Unit sits the aptly named Northern Unit, with 23 miles of groomed cross-country trails and 60 miles of snowmobile trails. Select campsites are also open here during the winter months.

Mojave National Preserve, CA
Mojave's 1.6 million acres were set aside to protect one of the most diverse desert environments in the world—a meeting of the Mojave, Sonoran, and Great Basin deserts. Inside its borders you'll find everything from sand dunes and volcanic cinder cones to Joshua tree forests and seven mountain ranges. If you're looking for solitude, Mojave is the place. Almost half the preserve is designated wilderness, where neither cars nor bikes are allowed. So the only tracks you'll see will be human ones…unless, of course, they're from bighorn sheep, mule deer, coyote, or desert tortoises.