Below me lies Crater Lake—a six-mile-wide oval so mesmerizingly blue and otherworldly that if the planet Neptune had lakes, they would look like this.

Tucked within a circle of jagged cliffs, the lake's blueness is so improbable that, according to local lore, it prompted one first-time visitor decades ago to write an angry letter to her congressman, accusing park rangers of lacing the lake with dye. It's that blue.

You can't blame her. Few places in the world have experienced the near-apocalyptic geological events necessary to create a freshwater lake of such extreme depth and clarity—a rare convergence of conditions that produced this cool color. Moreover, the federal government had the foresight in 1902 to protect this fragile ecosystem by making it a national park. That makes this year—the park's centennial—a particularly auspicious time to rediscover what poet Joaquin Miller christened "the Sea of Silence."

For all its renown, Crater Lake is one of those destinations that many people intend to see but never do. It gets only a fraction of the visitors who seek out other well-known parks, like Yellowstone or Mount Rainier. No doubt, Crater Lake's remoteness helps thin out the throngs.

(Portland, the nearest major city, is 250 miles away.) The notoriously short summers don't help either. The trails are generally snow free only from late July through October. During the other months, Crater Lake gets clobbered with nearly 50 feet of snow.

But perhaps the biggest deterrent is the misconception that Crater Lake is merely one more example of what the Pacific Northwest possesses in abundance—a sparkling body of water. And why drive all day for that?

That blasé attitude would have shocked late-19th- and early-20th-century travelers, who rightly regarded Crater Lake as one of the nation's great natural wonders. "It ranks with the Grand Canyon of the Colorado, the Yosemite Valley, and the Falls of Niagara," proclaimed National Geographic in 1897. World-class adventurers and artists such as Zane Grey, Jack London, Edward Curtis, and Charles Lindbergh all came to marvel. "Nowhere else had I seen such a shade of blue," declared Grey, after a fishing trip here in 1919. "It resembled the blue of heaven seen from the peak of a high mountain. . . . An amethyst in which tints of lavender and heliotrope were dominated by blue!" To read those early accounts is to see the danger that can occur when a thesaurus falls into the wrong hands.

Waxing rhapsodic while at the rim of Crater Lake may in fact be its visitors' most long-standing tradition. One individual able to resist that urge was Captain Clarence E. Dutton, a United States Army officer who escorted scientific expeditions to the lake in the 1880s. "The beauty and majesty of the scene are indescribable," he said simply—and accurately.

If you're going ... All phone numbers are area code 541. Sleeps Crater Lake Lodge, at Rim Village on the caldera's south rim. Rustic 1915 lodge overhauled in 1995. 71 rooms with lake and valley views. Reservations strongly recommended; heavily booked in summer. Open May 20 to October 20. 830-8700. Lost Creek Campground, south of Rim Drive on Pinnacles Road. 16 tent sites only. No reservations accepted. Mazama Village Motor Inn, in Mazama Village on park's south side. Forty motel units. Reservations recommended. Open June to mid-October. 830-8700. Mazama Campground, in Mazama Village. More than 200 campsites, some with hookups. First come, first served—no reservations accepted. Open mid-June through early October. Backcountry camping allowed throughout park. Free permit (available at Steel Visitor Center) required. Tasty Eats Crater Lake Lodge, Northwest-influenced breakfast, lunch, and dinner menu. Dinner reservations recommended. Open May 20 to October 19. 594-1184. Llao Rock Cafe, at Rim Village. Cafeteria. Open year-round. Watchman Restaurant, at Rim Village. Buffet-style dinners. Open mid-June through mid-September. Activities Boat tour to Wizard Island. Leaves 9 a.m. to 4 p.m. daily, from late June to mid-September. Departs from bottom of Cleetwood Trail, on north rim. Steep hike involved. Cost: $19.25 for adults, $11.25 for children. Centennial Celebration Events Crater Lake: A Tapestry of Inspiration, a symposium with educators, artists, American Indians, and park rangers sharing their insights about the park. October 4-6. Southern Oregon University, Ashland. Information: www.nps.gov/crla/symposium.htm. Crater Lake Centennial Exhibition, featuring park-inspired artwork by artists who participated in an artist-in-residence program at the lake. Through October 5. Schneider Museum of Art, Southern Oregon University, Ashland. 552-6245. Resolutions, a one-man play dramatizing Will Steel's colorful role in the creation of Crater Lake National Park. Various dates and locations around the state. Information: 594-3092. More Information Steel Visitor Center, on park's south side. Open 9 a.m. to 5 p.m., year-round. 594-3100. Rim Village Visitor Center. Open 9:30 a.m. to 5 p.m., mid-June through late September. 594-3090. Road and weather conditions and information: 594-3000,www.nps.gov/crla.

Those bygone visitors would be pleased to know that Crater Lake's splendor is still intact—and much easier to enjoy thanks to 33-mile-long Rim Drive (open to vehicles from mid-July to mid-October only), which encircles the caldera. Trekking along the rim by car or bike (or in winter on skis or snowshoes) is tantamount to strolling around a monumental ruin, like the Parthenon or Colosseum. Every overlook reveals new sights, such as 500-foot-tall totem pole-shaped rock formations teetering on the cliff faces; the basalt masts of the Phantom Ship, a volcanic remnant that juts out from the lake; the tiny islets that spill off Wizard Island.

For a balcony view, hike the mountains that crown the rim—notably Garfield Peak (1.7 miles to the top from an easy-to-reach trailhead), the Watchman (0.8 miles), and Mount Scott (2.5 miles). From those heights, you can watch the lake change color with the weather—from brilliantly blue under full sun to anything from pearl to gray under overcast skies.

To experience the lake up close, take the rather steep one-mile-long Cleetwood Trail, starting on the northern rim, to the water's edge. Once there, you can plunge in (the water is bracingly cold even in summer), fish for rainbow trout or kokanee salmon (no permit required), or hop a boat to Wizard Island. The island is home to 800-year-old trees and a breed of garter snake that has lost its distinctive yellow stripes to better blend in with the black lava. During the boat ride, keep an eye out for the Old Man of the Lake—a hemlock log that's inexplicably been bobbing around upright since at least the 1880s.

Surrounding the lake are nearly 200,000 acres of pristine backcountry—a kaleidoscope of landscapes that include pine and fir forests, a pumice desert, a sphagnum bog, and pinnacle-shaped volcanic formations straight out of The Lord of the Rings. This vast territory is so ignored by visitors that on a typical summer night fewer than 20 backpackers have it all to themselves.

The park's cathedral-like serenity is all the more remarkable for having been born of an explosion a hundred times more violent than that of Mount St. Helens in 1980. About 8,000 years ago, Mount Mazama—a volcanic peak that initially stood at least as tall as its Cascade cousins Hood and Rainier—had a major meltdown. After spewing ash as far as what is now Saskatchewan, the mountain's upper mile caved in, creating a caldera so deep that 19 Statues of Liberty stacked end to end would barely clear the rim. The caldera then sprouted a minimountain near its western edge (Wizard Island) and eventually filled partway with rain and snowmelt, creating present-day Crater Lake.

The Klamath Indians continue to pass down legends about how the lake was created—stories of a fiery battle between Llao, chief of the below world, and Skell, chief of the above world. In the end, Skell triumphed, cutting off Llao's head and tossing it into the lake—where, as Wizard Island, it still lurks. The lake was so sacred to the Indians that they successfully kept it a secret from pioneers until the 1850s.

When prospectors and soldiers did stumble onto it, each new group of "discoverers" christened it a different name before folks finally settled on Crater Lake (the rejects included Deep Blue Lake and Lake Majesty). One Gilded Age visionary—the aptly named Will Steel—felt such a spiritual connection with the lake that he waged a 17-year lobbying campaign to make it a national park. Ornery to the core, this self-styled promoter (famous in his day for organizing fireworks spectacles on top of Mount Hood) would chase politicians down the hallways of Congress to make his pitch.

In 1886, Steel signed on as a member of the first survey team to measure the lake's depth (a task they accomplished with a metal pipe tied to piano wire). Nearly 2,000 feet of wire was unspooled before the pipe touched bottom—ranking Crater Lake as the deepest in the United States and the seventh deepest in the world.

You'd have to go to Siberia, Africa, or northern Canada to find deeper freshwater—or to your bathtub to find a water level that fluctuates any less. The 34 billion gallons that enter Crater Lake annually as rain and snowmelt are offset by an almost equal amount lost through evaporation and seepage.

With no rivers leading in or out, Crater Lake is so free of incoming sediment that it's also one of the purest and clearest lakes in the world. The pilots of a research submarine that explored it in the late 1980s reported seeing faint sunlight on the bottom. (They also saw active thermal springs—indicating that Mount Mazama isn't extinct, just on simmer.)

And therein lies the secret behind the lake's astounding hue. Just as a prism splits sunlight into different bands of color, so does water. Reds and yellows are converted to heat close to the surface, while blues and violets penetrate much farther down and then scatter, creating a blue cast—an effect so drastically enhanced by Crater Lake's clarity and depth that on sunny days it resembles a luminous vat of ink. A mirror made of cobalt. I could go on, but why bother? As past generations have discovered, no amount of purple prose can capture that blueness.