In these days of superhighways and streamlined air travel, it's comforting to know that there still exist places where no roads lead and no jetliners land. Places like Nahanni, in the far western reaches of Canada's Northwest Territories.

Nahanni. The name alone conjures up powerful notions of Arctic mystery and legend. Located in the extreme southwestern corner of the huge province, where it closely hugs the Yukon border, the Nahanni region -- embracing the glacier-studded Selwyn and Mackenzie Mountains -- is abruptly bisected by the broad and powerful waters of the South Nahanni River.

The South Nahanni has everything a river can aspire to: big flows; exciting rapids; nearby hikes to alpine lakes; wildlife in the form of bear, caribou, fox, moose and Dall sheep; and just incidentally, a waterfall twice the height of Niagara Falls. The more my wife, Cherie, and I learned about the river, the more we began to dream about traveling it by raft. The fact that it is so hard to get to made the trip all the more appealing.

We had heard that the river was inaccessible except by bush plane, since there are no roads -- not even into Nahanni National Park, in which a portion of the river is contained. But the cost of a few-hundred-mile jaunt by bush plane is more expensive than a commercial airline ticket for our several-thousand-mile trip from the States. Besides, there's something a bit too easy and convenient about that course, especially if another possibility of access exists.

It does. There are two other ways to reach the river -- by trail and by water. The first involves a long overland trek across the Continental Divide and a descent to the Macmillan River, followed by poling upstream on several small streams before finally reaching the headwaters of the South Nahanni. With our hundred-pound raft and 200 pounds or so of boating equipment, not to mention food and gear, this option is out of the question.

The second alternative sounds a little more promising. It requires a rock-scraping, 40-mile float down a thin tributary called the Little Nahanni. And best of all, the source of this stream is accessible by road from Tungsten, a tiny mining town near the Yukon border. Suddenly things are looking up. It becomes our goal to float some 300 miles of the Nahanni, an adventure that will take us two weeks -- if all goes well.

As we unpack the boat and gear on the banks of the Little Nahanni, our expectations are high. I keep telling Cherie that this is only a "float" trip, nothing to worry about. And sure enough, the first day passes without a hitch. We spend the day maneuvering through a clear, cobblestoned stream, and set up camp early on a small gravel-bar surrounded by a sweeping wildflowered meadow.

The next day our troubles start. The rapids begin to increase in size, and the speed of the current doubles. Large sweeper trees with tentacle-like limbs lie across the river, narrowing our passage to a few feet. Armed with a set of sketchy guide notes and large-scale topographical maps, we keep coming to places we think we've already been. And supposedly the worst rapids lie ahead, in the three canyons of the Little Nahanni.

We pass what we believe are the canyons before arriving at what really is a canyon -- and it's only the first one at that. The steep walls soar up vertically on the left side, then the right. There is no portage route, no eddies, no nothing. The speed of the current is frightening, and the sound of the rapids reverberates off the canyon walls like a steam locomotive through a mountain tunnel.

The rock exposes smoothly formed, magnificently colored granite -- but I don't have time to enjoy it. The boat quickly fills with water, but there's no time to bail. Each drop cuts deeper than the previous one; the boat becomes a heavy beast to maneuver as it's pushed into hydraulics that threaten to flip us should we veer sideways. We round one blind corner after another, not knowing what unexpected abyss lies below. At last the canyon walls widen abruptly, allowing us to struggle to the shore, where we camp for the night. I spend a restless night, not helped by the sight of even worse rapids downstream.

Next on the agenda: a Class V rapids, which, our notes advise, should be portaged. We scout it at mid-morning, and because there's enough water to hide all but the biggest rocks, we decide to run it down the middle. We're thrashed about as the bow of the boat heaves heavenward, but finish right-side up. Cherie slowly turns around. "Just a float, eh?"

The Second Canyon appears later in the day, and while it's more open than the first, it has plenty of standing waves, which make for an exciting ride. The water is frigid! Then dark clouds invade the translucent sky to remove all traces of warmth. We pull over to add clothes and cram down a couple of granola bars, but it doesn't help.

The Third Canyon approaches. It looks easy from above, but once we're in it a big roily wave floods the boat to its rim.

We're still bailing and suddenly we're there -- on the South Nahanni. I expected an abrupt change, but the two rivers blend together unobtrusively. It's almost anticlimactic. The South Nahanni, however, is unlike its wellspring, the Little Nahanni. It's obviously wider, and although its silt-laden glacial current hurries us along for 70 miles until we hit the park boundary three days later, there are no rapids.

And a good thing, too, because now we can relax and enjoy the magnificent scenery. Dark gray mountain peaks are shrouded in a layer of snow and ice that renders the whole thing almost surreal. We're in the area of some of the finest technical rock climbing on the globe, known as the Cirque of the Unclimbables. The mountains are the Mackenzies, a northern extension of the Rockies, and their snow-crusted peaks, reflecting the streams of sunlight offered by a bleached blue sky, contrast sharply with the dark green of the forest beneath.

When we pull over to look around, we step onto -- more like into -- spongy moss and walk through a dense stand of sweet spruce and crooked poplars, littered below with decaying limbs and well-trodden game paths. We also see our first "snye" (a word we've seen in books on the North Country), which refers to a narrow channel of water branching off from the main flow of the river. The Nahanni is full of them, especially downstream, where taking the wrong turns means lots of rowing across dead water.

For the next week, we camp on islands in the middle of the river, a good idea for several reasons: The views are spectacular, unobstructed by the thick wall of trees lining the bank; driftwood for evening fires is always plentiful; and most important, the water should act as protection (we hope) against grizzly bears in the middle of the night. Still, the thought of ursine attack is never far from our minds (with each day providing 20 hours of sunlight and four hours of dusk, at least we'll be able to observe our attackers).

A few days later, floating down the river, we see a "grizz" foraging for berries on the bank. He's about 20 feet away and simply gazes at us with a perplexed but curious look, until we drift out of sight.

High on the right bank is Mount Sir James MacBrien, which at 9,059 feet is the tallest mountain in the Northwest Territories. The narrow chain of mountains encompassing this peak is fittingly called the Ragged Range, and the simple sight of glistening blue glaciers poured over stark stone -- rising straight up from the river -- is awesome. Nestled inside the range is an emerald gem, Glacier Lake, which can be reached by hiking along a clear, cold and fast-moving stream. Nearby are impressive mountains with first names as well as last -- Mount Sydney Dobson and Mount Harrison Smith.

Just downstream is a complete contrast: It's almost subtropical, with thermal water radiating outward from Rabbitkettle Hot Springs to form an intricately terraced mound of tufa rock more than 75 feet high.

We arrive at the boundary that marks the beginning of the park, and suddenly the current stops, with the boat hitting the motionless water as though it were a retaining wall. It's an equal opportunity trip: We've had white water, we've had fast current, now we have a lake -- 50 miles of it. Out come the oars, and for the next three days we inch the raft across the limpid surface of the river -- an act not unlike dragging a dead hippopotamus across a gravel bank, uphill. All the good campsites are inundated by the high water, and we're forced to camp on muddy banks infested with enough mosquitoes to drive even the most jaded sourdough insane.

The moose are a welcome diversion. They are seemingly everywhere along the river, their large racks held high, and each usually accompanied by a small calf. That evening we see a large bull moose upstream from our camp. He looks at us nervously and swims across the river (surprisingly, moose are excellent swimmers, even in deep, fast current). After reaching land, he walks downstream to cross the river once again, below us, and he trots upstream to complete his circle. He runs quickly into the woods, letting out a loud bugle.

Masses of textured gray and smooth purple clouds scurry in, reflecting the distant mountains in a shimmering molten gold. It's easy to see why they're called the Sunblood Mountains, and they signal our approach to Virginia Falls. We had worried about missing the cue and heading into the falls' big drop, but that seems silly now: At 410 feet, their height is more than twice that of Niagara Falls, so you hear the falls before you see them.

We pull over to shore, and the immediate impulse is to run down the portage trail to see the falls. Which is exactly what we do. They are spectacular, and no photograph or description can do them justice. We spend a lot of time that evening and the next day just watching tons of water rolling over rock. Naturally the first reaction of a river runner to the falls is a practical one: Are they runnable? The eyes search for a path through the maelstrom, but there is none. In its "quiet" beginning stretches, there are holes that would devour the 37-foot pontoons used in the Grand Canyon.

We reluctantly break ourselves away from the falling water for the inevitable portage around it. The portage trail is nicely constructed and the scenery is incredible, but somehow even that doesn't make the haul any easier. Next time I'm going to push the boat and gear into the falls and pick them up downstream.

Though almost as remote, the stretch of river below Virginia Falls contains more history of man's attraction to the river. First came the Indians. The Nahanni and Slave tribes of the Athabaskan Indians are said to have moved into the river's lower reaches in the 18th century after being driven out of their hunting grounds on the Liard River by the Cree. They lived a nomadic existence and left few traces of their presence. In fact, the name Nahanni is usually translated as "the people over there far away," which seems a perfect name for the river they lived on.

Not until the Yukon gold rush did outsiders begin to penetrate the valley, seeking another route to the gold fields. Most of the fortune seekers floated the Yukon River, but some ventured up the Nahanni, hoping to cross the Continental Divide at the river's source and then travel down the Pelly River to the gold mines. A few even speculated that gold could be found in the Flat River, a major tributary of the Nahanni, but despite the legends of big finds, their efforts ended in disappointment.

Our trip on the Nahanni is almost complete. In an eerie cloud of low fog, we drift slowly through abrupt sandstone canyons whose walls drip with waterfalls cascading from the rim somewhere above. We shuttle back and forth across the river, searching for the deepest current.

All too soon, it's over. We've reached "civilization": Nahanni Butte, a small Indian settlement where the Nahanni joins the Liard, which later joins the Mackenzie. Two days later, a friendly local drives us the 200 miles south to Fort Nelson, B.C., where our plane home awaits.

Suddenly it occurs to us what's happening: We're leaving the silence and beauty of the river for a bustling, artificial world. It's a cruel transition -- one I would rather not make. But we consider ourselves lucky, for at least we have tasted the waters called Nahanni. Cecil Kuhne is a freelance writer in Amarillo, Tex. WAYS & MEANS

While the Nahanni can be undertaken by experienced canoeists and whitewater rafters, commercial outfitters also run trips on the river. Among them:

Nahanni River Adventures (P.O. Box 8368, Station F, Edmonton, Alberta, Canada T6H 4W6, 403-439-1316). Guided trips include a nine-day Voyager canoe trip (17-foot canoes) costing $1,675 U.S. per person; a 12-day Voyager canoe trip ($1,775); a two-week national park trip via small canoes ($1,850); and a three-week whitewater trip ($2,395). Prices vary depending on the equipment needed. Fees are all-inclusive from Fort Simpson.

Nahanni Wilderness Adventures, Box 879, Nanton, Alberta, Canada T0L IR0, 403-646-5768.

White Wolf Adventure Expeditions (2565 W. Second Ave., Vancouver, B.C., Canada V6K IJH, 604-736-0664, or 634 Belvenia Rd., Burlington, Ontario, Canada L7L 4Z4, 416-681-6068). Scheduled guided trips for 1991 include 10-day raft and canoe trips at $1,751 per person, and a 14-day canoe trip at $1,972. Prices are all-inclusive from Fort Simpson. Trips are accompanied by a naturalist; brochures and videos describing the outings are available on request.

Blackfeather Wilderness Adventures (1341 Wellington St., Ottawa, Canada K1Y 3B8, 613-722-4229). Guided tours range from a one-week raft trip at $1,495 per person, a two-week canoe trip ($2,070) and three-week trips with whitewater canoeing or hiking options ($2,685). Prices are all-inclusive from Fort Simpson. Parties of five or more may arrange custom trips. GETTING THERE: There is no direct access by road to Nahanni National Park. Commercial air service is available by way of Canadian Airlines International (1-800-426-7000) to Watson Lake, Yukon, nearest the put-in, and to Fort Nelson, B.C., nearest the take-out.

Bush planes to the river may be chartered through Simpson Air Ltd. (Box 260, Fort Simpson, Northwest Territories, Canada X0E 0N0, 403-695-2505) or Liard Air Ltd. (Box 3190, Fort Nelson, B.C., Canada V0C 1R0, 604-774-2909). RECOMMENDED READING: Despite its remoteness, a fair amount has been written about Nahanni. "Dangerous River," by R. M. Patterson, has become the classic piece, and because it is written by a canoeist, is of greatest interest to river runners. Patterson explored the river by canoe, and the rest of the region by foot, in the late 1920s as a young college graduate from Oxford. His gentlemanly prose and simple lifestyle render it timeless.

Also of interest is Dick Turner's "Nahanni," written from the perspective of a trapper in the '40s and '50s. INFORMATION:

Nahanni National Park, Box 300, Fort Simpson, Northwest Territories, Canada X0E 0N0, (403) 695-3151.

Travel Arctic, Government of the Northwest Territories, Yellowknife, Northwest Territories X1A 2L9, 1-800-661-0788. -- Cecil Kuhne