You don't often think of Virgin and Las Vegas in the same breath, but a glance at a Nevada map shows that if you take the I-15 east out of the City of Conspicuous Bad Taste, you find yourself following the Virgin River upstream into southern Utah. After driving through sweeping passes and open plains, the river brings you finally to the little town of Springdale, at the entrance to Zion National Park.

If the American people may be accused of loving their parks to death, then Zion N.P. is currently in a stranglehold akin to the death-grip of a python. Consider the awful statistics. Last year, almost three million visitors poured into a valley just 10km (6 miles) long, and barely 500 paces wide at its broadest. That's over 5,000 vehicles per day in the summer months, fighting for just 480 parking spots.

The single lane road is so narrow there's nowhere to pull off, except in official parking spaces. And unless you stop, it's impossible to crane your neck back and appreciate the soaring red Navajo Sandstone walls that rise, in a thousand metre sweep, to the sky above, dwarfing everything around you.

This rising pressure of tourism, exhaust fumes and tempers has forced the park authorities into taking the drastic step of banning all private vehicles from April - October. During those months, courtesy shuttle buses (powered by propane to reduce pollution) roll up and down the valley, dropping off and picking up at nine different stops.

Trails are cut from cliff faces.

A good compromise leaves everyone dissatisfied, and this is no exception. The Canyon, one of the oldest of the red sandstone parks that cover much of southern Utah and northern Arizona (such as the Grand Canyon, Lake Powell, Bryce Canyon and Canyonlands) is the only one where such measures have so far been implemented. But if the trend continues, others won't be far behind. But wait, all is not lost! During the winter months, Zion is not only open to private vehicles, it is less crowded (indeed, often deserted). The air is bracing, and a dusting of snow decorates the huge monoliths of rock and stone, creating a fairyland of enchantment quite unlike that offered just a few hours away in Vegas. March is the best time. Snow still lingers on the top slopes, but the lower valley is clear, making walking doubly pleasurable. No one should visit the Canyon without making an effort to hike at least one of the cliff-hanging paths that were built during the post-Depression era, when gangs of laborers found employment in huge government-funded projects. We'll not see trails like those built ever again. Even a short gain in height allows the real spectacle of Zion Canyon to be appreciated. The path grades are gentle, the zigzags many, the effort minimal, and the rewards wonderful. If climbing ain't your thing, then drive to the end of the road (the Temple of Sinawava), where the valley is narrow enough for you to toss a pebble from one wall to the other. From the turnaround, a paved path leads 3km along the Riverside Walk to the Narrows. Looking beyond, a shallow creek trickles towards you over smooth pebbles, and you might be fooled into thinking you were almost at the source of the Virgin River. Think again. The upper reaches of this insignificant river drain hundreds of square kilometres. A sudden rainstorm, falling unseen miles away, can produce a flash flood that thunders unexpectedly down these slot canyons, sweeping everything before it. In 2000, a party of 15 hikers from Europe drowned in this way. If you go: Air Canada and Canada 3000 both fly into Las Vegas, the closest major destination. A rental car gets you to Zion in about 3 hours. Entrance fee is $20 per car, or $10 per person/cyclist. The pass is valid for 7 days re-entry. On the web, see http://www.zioncanyon.com/, or many other sites profiling the park. There is limited camping within the park - first come, first served. There's lots more in Springdale just outside the gates. The 1920s Zion Lodge (rebuilt in 1966 after a fire) is the only accommodation within the park. Book well in advance at (303)297 2757.