BIG BEND NATIONAL PARK, Texas — Craggy mountains, cactus-studded slopes, miles of meandering Rio Grande and a couple of born-again ghost towns at its edge, but Big Bend ranks among the National Park Service's least-visited parks, and that won't change any time soon.

The summers are infernally hot. Except for a handful of days a year, rafters can expect nothing more challenging than a Class III rapid. And if you're from outside Texas, getting here means flying to Midland or El Paso, then driving about five hours while deer, rabbits, coyotes, skunks, armadillos and javelinas scamper and shuffle in and out of your high beams.

But there is a payoff.

As the Rio Grande makes its way south and east through the Chisos Mountains — marking the Texas-Mexico border as it goes — the river frequently dwindles to 30 feet wide and as little as a foot deep, but the canyon walls leap up toward heaven. Most days, a child can cross the river in the right spot. But that same river can take a rafter to spots that are remote, rugged and gorgeous enough to satisfy even a well-seasoned desert traveler.

On the day we put in, the water was running 300 cubic feet per second, a flow so scant that the outfitter almost put us into canoes, which are better than rafts in shallow water. But we stuck with rafts and put in at Lajitas, about 10 miles outside Terlingua.

First, we drifted past boulders and tamarisks, a sipping horse here, a sunning turtle there. Then the earth began to ripple and rise on either side of us.

Of three major canyons that cradle the Rio Grande as it passes through Big Bend, the deepest is Santa Elena, an 8-mile passage that's inaccessible by road. And that was the heart of our itinerary, the stretch of water that awaited under those sudden 400-foot cliffs.

Awhile after we'd floated in, my raftmate Pamela Daggett of Austin got quiet.

"This is making me weep," she whispered.

In wonder and languor, we drifted along, four rafts in a deep declivity in the middle of nowhere. Guides Patrick Harris, Sandi Turvan and Darren Wallace told us about the 22 kinds of bats found in the canyon, the 1,200 kinds of plants, the 450 bird species. Fellow rafter Kelly Schievelbein of Seguin, Texas, who had thoughtfully packed pre-mixed Smirnoff cosmopolitans for the river, offered nips.

Despite the ideal weather, we spotted just one other rafting group. (In spring and fall, the temperatures along the river usually run 70 to 90 degrees by day, 45 to 60 overnight. Our trip was at the low end of that range.)

Everyone aboard was from Texas except me and Jon and Jodi Houlon, a Philadelphia couple, and most everyone had been hearing for years about the wonders of Big Bend.

The canyon swallowed us the next morning. Floating farther and farther in, we ate lunch in Mexico, which is a fancy way of saying we pulled off the river on the right side instead of the left. We skipped stones by the score, scrambled up a fern canyon for a mile or so, drained a few beers, saw nobody.

By the nightfall on our second camp, still miles from the end of the canyon, the looming walls had reduced the starry sky to a thin twinkling strip directly above us. And when I rose from my folding chair at the campfire to stretch my legs, there stood my shadow on the far wall, 75 feet high and flickering. Bright or dim, a handsome canyon.

"I thought it was going to be pretty, but it's just breathtaking," said fellow rafter Dottie Hall.

"I don't want to go to sleep," Jon Houlon said, "because then it'll be tomorrow."

But in the end he did, and it was. We broke camp, eased back into the slow flow and watched the cliffs stretch up to about 1,400 feet, then dwindle to nothing. We skipped a few hundred more stones into Mexico. (Somebody, check a satellite photo, and I'm sure you'll discover that Texas lost territory between Nov. 29 and Dec. 2.)

Then we turned a corner, and it was all over. The sky, that narrow sliver overhead from the night before, was big again. A telephone pole rose in the distance. You could see trails along the shore. Cars. People.