BOULDER, COLO. -- Each afternoon a stream of commuters pours into the mouth of Boulder Canyon, an extraordinary slash into the Rocky Mountains that begins at the edge of this Colorado university city. Some are headed home to Nederland, Gold Hill and other towns that are fast becoming bedroom communities; others are commuting to some of the best rock climbing in the county.

Boulder Canyon is one of the few places in the nation where a rock route is more apt to be crowded in late afternoon than in the morning. But why not, when you could get from a job anywhere in this city and be on the rock in 15 minutes to half an hour?

Boulder Canyon has all the comforts of home. And the rock is superb.

Among truly serious climbers, the canyon is passe. The rock gymnasts now gather in places like Smith Rock in Oregon or Hueco Tanks in Texas to put up the new routes that only a handful of people in the world can repeat.

By contrast, climbing in Boulder Canyon is like browsing in a familiar library: there is something for everyone presented in a comfortable setting. The card catalog is called "Boulder Climbs North," a guide book by Richard Rossiter.

Not that the crags, cliffs and buttresses that line most of the 15 miles of the canyon are necessarily easy. Most of them are not. New routes are still being established, but for the most part the rocks of the canyon were discovered and exploited years ago.

For intermediate climbers such as my son, Michael, and I, the canyon was full of delights.

When we headed west just after Memorial Day, we intended to sample the canyon and several other nearby climbing areas -- the Flatirons, huge slanting slabs that form part of Boulder's western skyline, Eldorado Canyon with its soft sandstone a few miles to the south, and the South Platte, a vast area of scattered buttresses southwest of Denver. By the time we left, we had spent one day in the South Platte and all the rest in Boulder Canyon.

It wasn't just a matter of the rock, which was a fine granite with a surface generally just rough enough to keep one's feet securely on tiny holds. It was the beauty of the canyon, the variety of the climbs and the convenience. For this town, the canyon is a little like having a gigantic jungle gym in the backyard.

The Potomac River Gorge at Great Falls is, by rock climbing standards, convenience itself. It is close to the center of Washington with many routes of varying difficulty. But the Gorge can't hold a candle to Boulder Canyon.

In the Gorge, all the routes are short. Here in Boulder there are some that require all-day efforts. Unlike Washington, the humidity is low. And here there is no poison ivy, which can be a greater hazard in the Gorge than falling.

To save money, we camped most of the time in a lovely, almost empty National Forest campground above Nederland at the western end of the canyon. It was free because the water system was not working, but that was no problem since we had water bags that we filled at Nederland's new visitor center.

Each morning we had a debate. Would we go down the canyon to Happy Hour Crag, Blob Rock or all the way to Elephant Buttress near the mouth? Or would we just stop again at Castle Rock?

A college friend of my son's, a beginning climber who lives here, joined us one day to do an easy climb of three pitches. On other days we did harder, multi-pitch climbs. And finally we spent considerable effort pushing ourselves to master Curving Crack, a difficult route whose crux was near the top. The only problem was that there was such a strenuous set of moves near the bottom that by the time I would get to the top my arms felt like lead.

While we were working on the route, a lean young man roamed the base of several other routes. He would climb a few feet off the ground and drop off before he got dangerously high. He had no one to belay him.

After Michael made it to the top of Curving Crack, I asked the young man if he wanted me to belay him on the route. He quickly nodded an assent. He turned out to be a peripatetic German whose American climbing partner had had to go back to work in Denver.

Foreign climbers swarm to American rock these days. On Happy Hour Crag we encountered two Frenchmen apparently so intent on doing each route on the crag that they had no time for idle chitchat with anyone.

The German climber was far more friendly and better on the rock as well. He moved effortlessly up Curving Crack with the balance and grace that marks a rock expert.

That is the unattainable goal I have set for myself: to be able to move with grace on rock. The reality is that I am not graceful. Like most of the world's climbers, all I can do is to try to lose weight, work out to make myself stronger and hope for the best.