Snowcapped mountains and deep, cool forests. Tumbling streams and a high, blue sky. Unfortunately, most travelers see this travel brochure scenery from the windows of their cars while speeding along I-70, which bisects Colorado.

But for those with a little extra time and energy, there's a wonderful alternative: an asphalt bicycle path that starts in the old mining town of Breckenridge and parallels I-70, on and off, for 42 miles, through the ski resort of Copper Mountain, to the town of Vail. On a recent weekend I made the four-hour trip with friends, fitness buffs who live in Aspen.

I'm a jogger and not in bad shape. But I'm a novice cyclist, and although the trip was very enjoyable, some of it was quite a challenge for me.

Or more precisely, a challenge for the muscles in my legs, which especially resented one part of the trip: the steep five-mile ascent up 10,660-foot Vail Pass. Even with the lightweight, 12-speed touring bike I was riding, I occasionally had to dismount and walk, while my companions pedaled furiously on.

The bike path, which has no official name, is maintained by the Summit County Road and Bridge Department in Breckenridge, the county seat, and Eagle County officials in Vail. There are five parking lots at entry points along the way, which are handy for short excursions. Although these are not marked, you can easily see the trail from many places along I-70.

The trail itself is well-marked and easy to follow, and cyclists never need to ride on a highway. Warning signs tell cyclists of upcoming sharp curves. No motorized vehicles are allowed, although we passed an occasional horseback rider. The fresh mountain air, scented by the pines, makes cycling on the path an invigorating experience.

My friends and I met on a Friday evening in Breckenridge and stayed overnight at the Fireside Inn, a bed-and-breakfast located in a rambling gray frame house a couple of blocks off Main Street, and a couple of miles from the Breckenridge Ski Area.

As ski towns go, Breckenridge could hardly be more different from Vail, our destination. Breckenridge was founded in 1860 and named in honor of John Cabell Breckinridge, then vice president of the United States, in hopes of improving the town's chances of getting a post office. (The spelling of the town's name was slightly changed after the VP joined the Confederacy during the Civil War.)

Originally, the town consisted of no more than tents, cabins and saloons. But it prospered from three gold-mining booms, and today Main Street is lined with authentic, 100-year-old Victorian-style buildings, many of which are now restaurants and shops. (Vail, on the other hand, was not established until about 1960, as a preplanned, almost instant alpine village of luxury condominiums and homes, and ski slopes favored by the international jet set.)

We started pedaling out of Breckenridge at 10 a.m. The path leaves Breckenridge along Main Street and the Blue River. Then it runs by an ugly but historical moonscape of gravel pits left behind by five giant, mechanical dredging boats, which mined gold in the river from 1898 to 1942.

Out of Breckenridge, the path runs along Highway 9, skirts the southern shore of Dillon Reservoir and enters a pine forest. For the next 10 miles, the path is mostly level and easy going all the way to Frisco, a touristy little western-style town with pleasant outdoor cafe's.

At Frisco Saturday crowds of families joined us on the path for a couple of miles, the only place the path was congested.

Frisco, which is right on I-70, is the starting point for a short bike trip up to Copper Mountain, seven miles west. This section of the path is generally level, and has some of the best scenery on the whole route. The path follows Ten Mile Creek, a stream that splashes down through pine and aspen groves. I kept trying to spot trout in the pools, wishing there was some way to ride a bicycle and fly-fish at the same time. We saw the first wildflowers of the season: red Indian paintbrush, golden banner and delicate western blue flag, similar to a garden iris.

We also saw the crisscross pattern of old mining roads high in the mountains, and distant slag piles marking the location of old mines. In summer the remaining high snow fields look like odd-shaped white sand traps on green mountaintop golf courses. In other places the snow clings to the sides of jagged gray peaks.

The trail winds along I-70, passing a place called Officers Gulch, where there is another parking lot, and then across Copper Creek golf course and into the ski resort of Copper Mountain. The path runs by empty, grassy ski slopes cutting through the trees on the mountain. Chairlifts hang motionless, as if waiting for next winter's crowds of skiers.

If you rode up from Frisco, Copper Mountain would be a good place to have lunch before pedaling back. You might try one of the outdoor cafe's with a view of the mountains, such as Vlasta's Cafe' in Snowbridge Square.

After Copper Mountain, the going gets tougher and the tough must start pedaling harder. The trail gains 1,000 feet of elevation in the five miles up to the summit of Vail Pass. At the summit we briefly lost the sun to clouds. At this elevation the air can be chilly even in midsummer, and we stopped to pull on the wool sweaters and windbreakers we had stuffed in our day packs.

There is a rest stop at the summit where travelers stretch, cyclists relax and fill water bottles, and everyone enjoys the mountain views. Here I caught up with my friends, who had left me behind on the climb up Vail Pass.

The reward for reaching the summit of the pass is the 20-mile glide down to Vail, a drop of 2,500 feet in elevation into the Vail valley. Soon we were riding practically through the back yards of some of the fanciest houses in Vail. At the Vail Golf Club I careened around a curve, barely missing an electric golf cart putt-putting along where the bike path crosses the course. Then we pedaled by the ski museum and into the center of the village.

We had arranged to stay overnight in Vail in another bed-and-breakfast, which turned out to be a condominium in the center of the village. That evening we ate at Los Amigos, a small Mexican restaurant popular with the locals. But we had to limit our consumption of margaritas and turn in early. Next morning we had to cycle back to Breckenridge -- and the climb up Vail Pass is much longer and harder on the way back. Robert C. Wurmstedt is a free-lance writer.