The King's Trail (cross-country skiing or hiking), 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).