GRAND CANYON NATIONAL PARK, Ariz. - About 4.5 million people visit this natural wonder every year, with relatively few venturing too far below the rim - where the trails along the cliffs offer constantly changing 3-D views that, quite simply, are otherworldly.
Even a short trek makes it clear why.
Temperatures in the inner canyon, a mile below the rim, soar well past 100 degrees much of the year, even though rim temperatures are cooler because of 6,000-to-8,000-foot altitudes. And unlike the typical downhill exit to most mountain ascents, the end of any climb in the Grand Canyon is always uphill - or in a helicopter if you're injured, sick or worse. More than 250 people are rescued every year.
"As beautiful as this place is, I think some people, perhaps, forget that it is a wild and rugged environment and, therefore, there are inherent dangers," said Shannan Marcak, park spokeswoman.
But for the well-prepared who are relatively physically fit, hiking is safe and offers an experience that's difficult to duplicate.
The South Rim is open year-round, although the trails can be covered with snow and ice on the upper elevations during winter yet still warm on the canyon floor. The North Rim is accessible in winter by skis. Most people hike in the spring and autumn because the desert environment is much cooler than summer.
Even in early fall, the high temperature hit 110 on the bottom when I set out with my wife, brother and his wife for our first trek of this wonder.
We went down the expansive 7.2-mile South Kaibab Trial from the South Rim, stayed two nights in one of the four-person cabins at the historic Phantom Ranch and then hiked out the 9.6-mile Bright Angel Trail, both of which connect to the North Kaibab Trail that leads to the North Rim. Bright Angel is also a good trail for short day hikes.
The trails are narrow and relatively steep, but there aren't any vertical climbs. The hardest part is near the top.
The view is breathtaking from the rim, and the layers of earth are easy to see, but hiking through those strata and the various formations gives you a close-up view. Every switchback offers a different, overwhelming scene. The changes are also visible by the different colored dust that collects on your shoes: tan, then red, then another shade of brown.
"It keeps unfolding like a puzzle," my brother observed.
Geology was never so interesting.
The erosion that created the canyon deposits silt into the Colorado River, giving it a red hue much of the year.
"This river's nature is to be red and full of sediment," Marcak said.
Besides the coolness of the morning, hiking early also lets you see the shadows advance along the landscape as the sun treks across the sky.
At night, there is no light pollution on the bottom of the Grand Canyon, so the stars shine brightly and the constellations are clearly visible. We hiked out before dawn and found headlamps are helpful but even a half-moon offers more than enough natural light to see the trail - and clear views of the river that rushes far below on two bridges.
It's one of those moments you take in and recall again and again after the trip: You're under the heavens on the bottom of the Grand Canyon and the only natural sound is the rush of the Colorado River.
"The vastness of this is literally overwhelming to many people. I think some people are really struck with their insignificance," Marcak said.
One of the hikers we met on the trail was Bob Stevenson, 67, of Boss, Mo., who rode down the Grand Canyon on a mule with his wife in 1995 and had returned with his adult son.
The mule ride wasn't as taxing physically, but hiking gave the father-son team a chance to linger on the trail, take it all in and spend some quality time, he said, comparing the only two ways to get to the bottom on land.
"I think the hiking just gave you an opportunity to get a better feel for the canyon itself because you could stop and look. And we had the squirrels getting in our backpack and the ravens all around us. It was pretty neat," said Stevenson, a retired accountant.
He thought he might be the oldest hiker but saw people years his senior.
"If you're in reasonably good shape and understand what you're getting into and have plenty of water and train for it, then it's very doable," Stevenson said.
Next to actually hiking, the biggest challenge is getting reservations.
There are two options for overnight stays on the canyon floor: the cabins or dorms at Phantom Ranch or one of the three campgrounds - Indian Gardens, Bright Angel and Cottonwood. Combined, that means there are only several hundred people staying in this part of the canyon at any time. The campgrounds require a backcountry permit; the ranch does not.
A year out, my brother secured us bunks at the men's and women's dorms at the ranch - a 1920s-era spread that serves as an oasis for hikers, mule riders and rafters - but we were able to get a cabin once we arrived by checking in with the office on the South Rim.
It's like going back in time.
You're truly isolated and can't just run to town for something. Supplies come by mule. Breakfast and dinner reservations are required ahead of time. There's no cell phone signal, television or Internet, which provides a much-needed break from the daily constant of flickering screens. A book, card game or just good conversation are the main sources of entertainment.
Here, social networking entails asking others about the hike down or hearing from veterans who have done the trip before.
Finding out which team won Monday night football proved to be a challenge, especially when we asked European tourists.
There is a pay phone but we didn't use it. The kids were with grandma.
The canteen at Phantom Ranch is a community gathering place for its temporary residents. Besides breakfast, the dinner menu is limited to two meals that are served at alternating times each evening: steak and hiker's stew. The dinner bell usually beckons guests, most of whom are already waiting outside for the door to open. At other times, the canteen is a place to cool off and converse. And every afternoon, red-faced hikers start arriving and head to the water cooler.
Bright Angel Creek, which snakes along the bottom of the canyon next to the ranch, also provides a great place to cool off, rest sore muscles - and look up to survey where you'll be hiking in the morning.
Grand Canyon: www.nps.gov/grca
South Rim Village: Located about 90 miles northwest of Flagstaff, Ariz. Other nearby attractions include Monument Valley and the Hoover Dam.
Phantom Ranch: Reservations for meals and lodging at Phantom Ranch, at the bottom of the canyon, can take up to 13 months:
phantom-ranch-704.html. Day hikers and guests of Phantom Ranch don't need permission to go below the rims, but anyone spending the night in a campground must have a $15 backcountry permit that can be obtained up to four months in advance by faxing a request. Details at www.nps.gov/grca/planyourvisit/
Safety tips and other information: www.nps.gov/grca/planyourvisit/
•Drink 1/2 to 1 quart of water or sports drink every hour of hiking. Not every trail has potable water stops and not all of them are open year-round, so check with the Park Service. Sports drinks are available in powder, so all you need to do is add water. For coffee drinkers, Starbucks makes an instant coffee, Via, that dissolves in water and actually tastes good.
•The earlier you go, the cooler it is. You can make a lot of good time in the dark; even with a half-moon it was possible to see well enough without a headlamp. And you're ready to take advantage of the rich morning light for photos and videos.
•Phantom Ranch sells snacks at its canteen, so you can buy some there for the trip back up.
•Watch the time, since it takes about twice as long to hike up as it did to go down. The Park Service recommends against hiking to the river and back in a day - let alone from rim to rim. Heat, distance and steep trails can overcome the strongest of hikers.
•Pack as lightly as possible. Water and snacks should be the heaviest items in your pack.