As the Midnight Sun Express begins its journey northward from Anchorage, one fact quickly becomes apparent: This is no express.

But as the train winds slowly through forested mountain passes, over bridges hovering nearly 300 feet above creek beds, past shimmering lakes and willows where moose munch on tender new vegetation, passengers relish every moment.They will spend 7 1/2 hours traversing 233 miles.

And they will spend the rest of a lifetime remembering that first sighting of Mount McKinley - Denali, the natives call it - soaring 20,320 feet toward the heavens. Few will soon forget their visit to Denali National Park and Preserve, the vast wilderness over which it towers.

Witnessing even part of the mountain's grandeur is an experience shared by only about 30 percent of the park's visitors. Usually shielded by a thick cloud cover, never closer than 46 miles from the rail tracks and even more distant from the park's one roadway, Denali reveals itself only on that rare picture-perfect day.

This is that day.

The mountain stands within a park that encompasses nearly 6 million acres - bigger than the state of Massachusetts. Established in 1917 to protect and preserve one of North America's greatest concentrations of wildlife, it was opened to the public in 1923 with the completion of the Alaska Railroad. Park boundaries were expanded in 1980 beyond its original 9,300 square miles.

Even when confined to a tour bus along the narrow roadway, visitors see herds of caribou moving over open tundra and slopes, Dall sheep grazing in an alpine meadow and huge grizzly bears standing guard as their yearling cubs wrestle playfully in the grass.

These animals share their homeland with wolves, hares, porcupines, marmots and 161 species of birds that live here year-round as well as others that come from as far away as Hawaii and South America to raise their young.

More than 450 species of trees, shrubs and herbs survive winter temperatures that plummet to 50 degrees below zero. By June, the tundra is alive with color.

Most cruise-tour passengers stay only a day or two. They arrive on the Midnight Sun Express, then continue their excursion another 123 miles northeast to Fairbanks.

Even a brief visit brings rewards. Most Princess cruise-tour participants spend evenings at the delightfully rustic Denali Princess Lodge a short drive from the railroad station near the park entrance.

They tour the Alaska range by helicopter or fixed-wing aircraft, take a wilderness safari by jet boat or join a guided rafting excursion through rugged whitewater canyons - each lasting four hours or less.

Or they arise before dawn and embark on a seven-hour wildlife search 20 miles into the park by bus.

The latter provides a good introduction to Denali's wonders. But with dozens of buses traversing the same road, it also yields frustration.

Too often, just as a caribou moves within sight, a guide insists, "We must go to make room for the next tour group."

Some visitors travel by bush plane 30 miles into the park to Denali Wilderness Lodge (a $175 day excursion over glaciers, with a meal and nature walk included on Princess tours).

Overnight accommodations for 48 guests are available in the main lodge and nearby cabins, though cruise-tours generally don't offer this option.

From early June until early September, independent travelers can overnight near the base of the mountain at Camp Denali nature center or North Face Lodge, both accessed by bush plane. Accommodations are far from luxurious - Camp Denali has a central shower room - and prices are steep. But guests delight in telling of spectacular views from the heart-shaped peepholes of outhouses.

Whatever activities are undertaken within the park, getting there on the Midnight Sun Express is a treat.

Don't be confused by brochures touting Princess' Ultra-Dome coaches, Holland America's McKinley Explorer cars and the public coaches of the Alaska Railroad. All are part of one long train. Yet each is distinct in appearance.

The two-story Ultra-Domes are the largest passenger rail cars in existence. Passengers sip beverages at their assigned seats, feast on gourmet cuisine in individual car dining rooms and watch the ever-changing scenery from open-air observation platforms.

If Denali is on display, the train slows almost to a halt.

It's a one-of-a-kind express.