You've already become acquainted with Arches National Park simply by driving Utah's highways: Delicate Arch is pictured on almost every state license plate. Delicate may be the most famous sandstone formation, but it's got plenty of company: The park has the world's highest concentration of natural arches—almost 3,000 have been identified in the flaky sandstone so far. (To be officially designated an arch, the light opening must measure at least three feet in any direction.) This is a pocket-size national park—just 73,000 acres, with a single paved road running its length—so it's hard to avoid the crowds. The park is open around the clock, and the sun rises between 6:30 and 7 A.M. in spring and fall. Late risers should be at the entrance no later than 8:30 A.M. Pack a lunch to bring into the park, from either the Red Cliffs Lodge (lunch, $9) or the Red Rock Bakery & Net Café (74 S. Main St.; 435-259-5941; box lunches, $12).

The road through Arches takes you past some spectacular natural sculptures, formed by the forces of wind and water working on millions of years' worth of compressed sandstone. Those brown and black patches? They're "desert varnish," a conglomeration of windblown clay and oxidized manganese and iron. The stunted trees are junipers and -piñon pines—the latter of which produces pine nuts. You can skip the visitors center, but there's one thing you must know: Walk only on trails or slickrock (which is slick only to horses' hooves, not to rubber soles or tires). Much of Arches, and indeed much of the territory you'll be traversing on this trip, is covered by cryptobiotic soil—a crust of algae, lichen, mosses, micro-fungi, and bacteria that keeps the dirt below from eroding. The motto here: Take only pictures, leave not even footprints.

Just a mile or two from the park entrance, you might want to pause for a picture of Sheep Rock, to your left, but hold off taking photos of the formations on your right: They're better admired in the afternoon light. Continue about 17 miles to the end of the road. From here, the Devils Garden trail takes you past seven arches in just over four miles—the best-known is Landscape, which lost a 60-foot-long slab in 1991 (some geologists think this has actually extended the life of the arch, since it reduced the weight of the suspended stone). From the Double O Arch, you can turn onto the Primitive Loop back to the parking lot, but much of this trail is a long slog and you're better off saving your energy for later. Instead, head back the way you came and have lunch on one of the tables near the trailhead.

At 3 P.M., make your way down to the Fiery Furnace Viewpoint, where you'll be meeting Matt Moore, owner of the guide service Desert Highlights (800-747-1342; deserthighlights.com). Despite its name, the Fiery Furnace is one of the cooler sections of the park, a mazelike cluster of red sandstone "fins" (or flames, in the right low light) with cracks just wide enough to shimmy through. Welcome to the sport of canyoneering. This area of Arches is off-limits to the public—you need either to go on a ranger-led group tour, to have route-finding skills and obtain a permit from the National Park Service, or to go with a guide like Moore, who'll lead you deep into the Furnace, where the only sounds are from the piñon jays overhead, and take you on as rugged a canyoneering adventure as you want. Not to worry if you don't have climbing experience: He's used to clients who don't know how to tie anything other than their shoelaces.