Imagine another Yosemite Valley, only 10 times larger and with a great river running through it, with twice the flow of the Nile.

The Columbia River Gorge, between Oregon and Washington, is just such a place. And if it had not been settled and its river used for commerce from its earliest discovery, it would have been a cinch to be made a national park.

Even so, it is still a National Scenic Area and runs 80 miles from near rain forest in the west to near desert in the east. It is a scenic prodigy.

Mt. Hood

You can see its immensity best perhaps from the air. Flying up the Willamette Valley into Portland, Ore., the Cascade Mountains stretch out to the east like a great rumpled bedspread, green with trees. Above the range are the white, snowcapped cones of the huge volcanoes — the Three Sisters, Mount Jefferson and Mount Hood, piled Ossa-on-Pelion above the greener peaks below.

As the plane turns west to land, you can see the Cascades continue north to Canada, and the white pyramids piled on top include Mount Adams, Mount St. Helens and, way out on the horizon, the biggest of all, Mount Rainier.

But gouged out of the mountains, running east and west in the space between Hood and Adams, the gorge looks like a giant slice taken from the middle of a continental meatloaf.

From the air, you can get some sense of the proportions of the gorge. It becomes easier to understand the geological processes that formed it, from the greenish Ohanapecosh Formation of mostly metamorphic rocks, some 40 million years old, to the many basalt flows and volcanoes that poured through the mountain valleys.

Most astonishing might be the great floods that tore through the gorge during the Ice Age, some 15,000 years ago.

Melting water had backed up across Idaho and Montana behind a dam of ice half a mile high. When the dam broke, 500 cubic miles of water — a fifth the volume of Lake Michigan — churned across eastern Washington and through the narrow gorge. Water left its mark 1,000 feet above the present-day city of The Dalles.

The Dalles

It is hard to comprehend the strength of the water. Nearly 10 cubic miles of water poured through the valley every hour for more than 40 hours — 10 times the flow of all the rivers in the world combined. It washed eastern Washington bare, leaving behind the area we now call the Channeled Scablands, still largely naked rock.

The Scablands

The ice dams reformed and rebroke as many as 100 times. Geologists believe the floods occurred on average about every 55 years for 2,000 years, widening and reshaping the Columbia River Gorge into its current U-shape.

Indians lived along the river as long ago as 10,000 years. Europeans first sailed up it shortly after the American Revolution and an American named the river after his ship, Columbia Rediviva, in 1792.

But it was the Lewis and Clark Expedition that literally put the river on the map.

The expedition followed the river to the coast in 1805 and camped there over winter, looking for a clear Northwest Passage from the East Coast to the West Coast.

By 1840, the Oregon Trail brought hordes of immigrants to the area, looking to farm and build new cities.

They came down the river, by road where possible, but across the watery rapids in the tighter sections where no roadbed was possible.

Nowadays, Interstate 84 follows the river’s south shore, or Oregon side, but it wasn’t until 1913 that anyone tried to find a way to build a continuous road through the gorge. 

That road, the Columbia River Gorge Scenic Highway, has been superseded and largely obliterated by the interstate, but sections of it are still driveable — 22 miles from Troutdale to Dodson and nine miles from Mosier to Rowena.

You can get the big picture from the air, but to really know the beauty of the gorge, you need to be on more intimate terms, and the remnants of the old highway — now called the Historic Columbia River Highway — are the best way to do that.

Beginning in Troutdale, you drive across the Sandy River toward Springdale. The road stays on the back side of the ridge, so you cannot see the river until you get to Portland Women’s Forum State Park, where a small parking lot affords a grand view up the gorge. You are on a bluff some 700 feet above the water, and the mountains pale into powdery blue as they recede. In the rake of morning light, it looks like a Chinese ink painting.

A mile or so down the road, the next outlook comes at Crown Point and the historic Vista House built in 1916. The octagonal building serves as a visitor center for the gorge and has exhibits and a very good gift shop.

View from Crown Point

It also has views for 30 miles in each direction.

The highway climbs down the river side of the ridge and begins to follow the water and the interstate. Nevertheless, this section from Latourell Falls to Horsetail Falls is the highlight of the trip.

The river is lined with a thousand-foot cliff, some 10 miles long, over which cascade more waterfalls per mile than any place in the world outside Hawaii.

They jump off the top of the cliff and pour, almost in slow, misty motion, to the pool below. With names like Mist Falls, Bridal Veil Falls and Punch Bowl Falls, they give you a sense of almost tropical richness.

Multnomah Falls

Indeed, just above the most famous of them, Multnomah Falls — with its parking lot and lodge — sits Larch Mountain, where the annual rainfall is 200 inches.

Another 50 miles down the gorge, at The Dalles, the rainfall drops to 12 inches a year.

The best view of the dry, eastern end of the gorge is from Rowena Crest, where an overlook sits like an aerie over the dry basalt hills near The Dalles. Grass is yellow in the summer, and you sometimes can look out over the shoulders of hawks.

The eastern end of the gorge also can be quite hot. In July, the temperatures easily can top 110.

If you continue east on Interstate 84, past the Deschutes River, you can cross the Columbia on the Sam Hill Memorial Bridge at Biggs.

Once across and in Washington, there are two other Sam Hill monuments you should see.

Hill was the Washington mover and shaker who managed to get the early highway built. He also constructed a mansion for himself out in the blasted rocky grasslands. He called it Maryhill, and it is now an art museum with a respectable collection of work, specializing in Russian icons, art chess sets and the sculpture of Rodin.

But the oddest Hill monument is the concrete Stonehenge he built in 1918 as a memorial for the war dead of Washington’s Klickitat County. The imitation Stonehenge was meant to look like the original did when new, so it has a strangely antiseptic look, without the patina that age gives history. 

Coming back through the gorge on the north shore along Washington 14 — known as the Lewis and Clark Highway — you retrace your route with a whole different look. The desert gives way to the trees, and the smaller road twists around headlands and coves.

At Stevenson, Wash., the Columbia Gorge Interpretive Center has exhibits not only on the geography of the area but also its history and culture.

And near North Bonneville, the great Bonneville Dam blocks the river flow in five disjointed segments between four islands. It was one of the great public works projects of the Great Depression and opened in 1938.

Bonneville Dam

There are modern visitor centers accessible from each shore.

The Bradford Island Visitor Center, reached from the Oregon side, is the larger, but the Washington Shore Visitor Center has the better view of the powerhouses with their huge generators.

Further along, Beacon Rock stands like a giant upended football, 848 feet high, with a hairpin stairway up its side for adventurous climbers. It was named by Lewis and Clark and marks the beginning of Columbia River tidewater.

Beacon Rock

The final monumental attraction of the trip is the skirting of Mount Pleasant and the section called Cape Horn, where the road barely holds onto the rock wall. Several turnouts offer a final glorious view of the gorge.

All along the way, there are state parks and nature preserves. Wildflowers are startling, hiking is popular and so is bicycling.

And above everything, you get the occasional unblocked view of white-headed Mount Hood, a beautiful, symmetrical volcano that is the symbol of the area.