Fossil Exhibit Trail and Cliff Shelf Nature Trail are must-dos, but even these popular trails are primitive, so don't expect to see bathrooms or any hiking surfaces other than packed dirt and gravel. Because the weather here can be so variable, rangers suggest that you be prepared for anything. Wear sunglasses, a hat, and long pants, and have rain gear available. It's illegal to interfere with park resources, which includes everything from rocks and fossils to plants and artifacts. Stay at least 100 yards away from wildlife. Because of the dry climate, open fires are never allowed. Tell friends, relatives, and the park rangers if you're going to embark on a multiday expedition. If you have a cell phone with you, assume that it won't get a signal in the park. But most important of all, be sure to bring your own water. Sources of water in the park are few and far between, and none of them are drinkable. All water in the park is contaminated by minerals and sediment, and park authorities warn that it's untreatable. If you're backpacking into the wilderness, bring at least a gallon of water per person per day. For day hikes, rangers suggest you drink at least a quart per person per hour.

Easy

Fossil Exhibit Trail. The trail, in place since 1964, has fossils of early mammals displayed under glass along its ¼-mi length, which is now completely wheelchair-accessible. Since October 2006, the trail has new fossil casts that are touchable. Give yourself at least an hour to fully enjoy this popular hike. 5 mi northwest of Ben Reifel Visitor Center on Hwy. 240.

Window Trail. This 200-yard round-trip trail ends at a natural hole, or window, in a rock wall. Looking through, you'll see more of the distinctive Badlands pinnacles and spires. 2 mi north of Ben Reifel Visitor Center.

Moderate

Castle Trail. This easy hike stretches for 5½ mi one-way from the Fossil Exhibit trailhead on Badlands Loop Road to the parking area for the Door and Windows trails. If you choose to follow the Medicine Root Loop, which detours off the Castle Trail, you'll add ½ mi to the trek. If you plan to walk the entire trail, give yourself three hours—slightly more if you want to take extended breaks. Experienced hikers will do this one more quickly. 5 mi north of Ben Reifel Visitor Center.

Cliff Shelf Nature Trail. This ½-mi loop winds through a wooded prairie oasis in the middle of dry, rocky ridges and climbs 200 feet to a peak above White River Valley for an incomparable view. Look for chipmunks, squirrels, and red-wing blackbirds in the wet wood, and eagles, hawks, and vultures at hilltop. Even casual hikers can complete this trail in far less than an hour, but if you want to observe the true diversity of wildlife present here, stay longer. 1 mi east of Ben Reifel Visitor Center.

Door Trail. The ¾-mi round-trip trail leads through a natural opening, or door, in a Badlands rock wall. The eerie sandstone formations and passageways beckon, but it's recommended that you stay on the trail. The first 100 yards of the trail are on a boardwalk. Even a patient and observant hiker will take only an hour here. 2 mi east of Ben Reifel Visitor Center.

Notch Trail. One of the park's more interesting hikes, this 1½-mi round-trip trail takes you over moderately difficult terrain and up a ladder. Winds at the notch can be fierce, but it's worth lingering for the view of the White River Valley and the Pine Ridge Indian Reservation. If you take a couple of breaks and enjoy the views, you'll probably want to plan on spending a little more than an hour on this hike. 2 mi north of Ben Reifel Visitor Center.

Difficult

Badlands Wilderness Area. If you want a challenge, you might consider trekking this 100-square-mi parcel of grassy steppes and rocky canyons east of the highway and south of Sage Creek Rim Road, near the Pinnacles entrance. There are no services here and very few visitors, even in summer. Before venturing out, check in with park staff at one of the visitor centers. 25 mi northwest of Ben Reifel Visitor Center on Hwy. 240.

Saddle Pass Trail. This route, which connects with Castle Trail and Medicine Root Loop, is a steep, ¼-mi climb up and down the side of "The Wall," an impressive rock formation. Plan on spending about an hour on this climb. 2 mi west of Ben Reifel Visitor Center.

Gear Up!

Located in the Rushmore Mall, Scheels All Sports is an everyday, all-purpose outfitter. Whatever outdoor activity you have in mind, Scheels provides equipment and advice for locals and visitors alike. Whether it's for golf, paintball, biking, or hiking, Scheels offers top-of-the-line equipment at only slightly inflated prices. At this writing, Scheels was planning to open a larger store a few miles east, just off Exit 60 along I-90, of its current Rapid City location in Spring 2009. 480 Rushmore Mall, 2200 N. Maple Ave., Rapid City. 605/342-9033. www.scheelssports.com.