Spend four days and three nights on the Appalachian Trail with REI Adventures. This vigorous outing follows the trail through the Great Smoky Mountains National Park, and is a good challenge for fit beginners who are ready to learn from the guides. Be ready for some flexibility in the trip itinerary. You might hike up to 13 miles in a day, depending on availability for the primitive trail shelters you’ll stay in along the way. Cost: $700/775 (REI member/non-member) in 2015, rising to $749/824 (member/non-member) in 2016.