Go here: Glacier National Park, Mont., 2.16 million annual visitors
Skip: Rocky Mountain National Park, Colo., 3.23 million annual visitors
Why Glacier: At nearly four times the size of Rocky Mountain, Glacier has plenty to see. Start with Going-to-the-Sun Road, a 50-mile drive that winds through the park's most dazzling scenery. (Weather can affect which sections are open. Check ahead.)
Later, strike out on some of the park's 700 or so miles of trails. The two-mile Avalanche Lake Trail is a popular hike that can be done all season, says Becky Lomax, author of the Moon Glacier National Park guide.
Need another reason to go? The park now has only 25 glaciers, down from 150 in 1850.
How to save: July and August are the busiest and most expensive time at Glacier, so visiting in late spring will turn up the best deals, says Michael Greenwald of Fort Lauderdale's Personalized Travel agency.
In the first half of June, a balcony room at Glacier Park Lodge, located less than a mile outside the park, starts at $167, down from $189 in midsummer. Tours are also less expensive in the spring. Tauck, for one, offers June departures of its nine-day Canadian Rockies and Glacier National Park outing for $3,990 -- at the height of the season the same itinerary costs $4,390.
They soar above ordinary trips and perform feats of vacation derring-do, all while nailing their budget. Here are their travel tips.