Fasten your seat belts, folks. We're headed into southwestern Colorado's "skyway" country. If you like roller coasters, this is the drive for you. Edging potentially perilous drop-offs, the roads we'll navigate soar, plunge, and twist in tight curves mile after mile. Many of you are apt to get a bit rattled (I always do). But the reward is some of the most spectacular mountain scenery in America.

Fortunately, you don't have to pay theme park prices for the scenic thrills. This roller-coaster adventure-a four-day, 1,000-mile excursion into the massive San Juan Mountains-definitely rates as budget travel. Expect to pay from $50 to $80 a night in a good chain motel. And dine cheaply on the local ranch-house staples: juicy prime rib and sizzling grilled steaks.

A range of the Rocky Mountains, the San Juans boast more than a dozen peaks that rise to above 14,000 feet. Sprawling across 10,000 square miles, they make a majestic but sometimes intimidating realm best seen on a 233-mile loop called the San Juan Skyway. An officially designated U.S.D.A. Forest Service Scenic Byway, it climbs in dizzying switchbacks over 11,008-foot Red Mountain Pass-the high point on the loop. In late spring when I last tackled the ascent, the summits around me were still cloaked with snow.

Break up the drive with plenty of outdoor action. Hike, bicycle, go white-water rafting or kayaking, fish, ride a horse, try rock climbing. This is the place for it.

Getting started

Denver's low airfares are not surprising. It is served by several discount airlines: America West, ATA (American Trans Air), Frontier, JetBlue, and Spirit Airlines.

Another incentive to book into Denver is that car-rental rates there tend to be cheaper. Using the Internet, the least expensive rental I could find in Montrose cost about $40 more a week than a similar rental in the Colorado capital. Many of the rental agencies in Montrose impose a mileage limit, which also might have added to my cost. For a one-week, midsummer rental of an economy-class car out of Denver, the various national car-rental brands quoted between $150 and $200 (with unlimited mileage). (Lodging rates below are for two people for one night during the peak summer season.)

On the road

Day one

Denver via Glenwood Springs to Grand Junction, 265 miles. As your plane descends into Denver, take a look at the peaks rising west of the city-in about an hour, that's where you'll be.

Usually I try to avoid interstates, but I-70 treats you to a dazzling introduction to the Rockies. About 60 miles west of Denver, the highway climbs to above 11,000 feet as it passes through the Eisenhower Memorial Tunnel, reputedly the highest auto tunnel in the world. Beyond is the famous ski resort of Vail; stretch your legs as you stroll along its ersatz alpine streets.

I-70 snakes alongside a number of tumbling streams, but it's the Colorado River that puts on the best show as it races for a dozen miles through the steep rock walls of Glenwood Canyon. A thrilling drive; you can almost imagine you're bouncing down the river on a white-water raft. Take another break at the giant hot-spring pool (adults, $13) in the center of Glenwood Springs, a bustling resort town.