Hiking

Your most memorable Yellowstone moments will likely take place along a park hiking trail. Encountering a gang of elk in the woods is unquestionably more exciting that watching them graze on the grasses of Mammoth Hot Springs Hotel. Hearing the creak of lodgepole pines on a breezy afternoon feels more authentic than listening to idle tourist chatter as you jostle for the best view of Old Faithful on a recycled-plastic boardwalk for 94 minutes or so.

Even a one-day visitor to Yellowstone can -- and should -- get off the roads and into the "wilderness." Since the park is a wild place, however, even a half-mile walk on a trail puts you at the mercy of nature, so be sure to prepare yourself accordingly. As a guide on an Old Yellow Bus Tour said, "You don't have to fear the animals -- just respect them."

Outfitter & Expeditions

If you are interested in having a park expert, whether a naturalist, geologist, or wildlife specialist, accompany you, the Yellowstone Association Institute offers daylong hiking excursions; multiday "Lodging and Learning" trips geared around hikes, some of them designed for families (there are age restrictions on some trips); and full-blown backcountry backpacking trips. The Lodging and Learning trips include nightly accommodations at park facilities, but for the hikes you bring your own personal gear; they provide group gear and instruction plus permits as needed and some meals. The association also offers courses on topics ranging from nature writing to wolf biology. Taught by college professors or other experts, most courses are for people age 18 and older. Box 117, Yellowstone National Park, WY, 82190. 307/344-2293. 307/344-2486. www.yellowstoneassociation.org. From $80 for 1-day trips to $1,000+ for 5-night trips, including lodging.

Easy

Back Basin Trail. A 1.5-mi loop passes Emerald Spring, Steamboat Geyser, Cistern Spring (which drains when Steamboat erupts), and Echinus Geyser. The latter erupts 50 to 100 feet every 35 to 75 minutes, making it Norris's most dependable big geyser. Grand Loop Rd., Norris. Easy.

Cascade Lake Trail. This 4 1/2-mi round-trip trail loops around Mud Volcano and seething, sulfuric mud pots like Black Dragon's Cauldron. Grand Loop Rd., 10 mi south of Canyon Village. Easy.

Fountain Paint Pots Nature Trail. Take the easy 1/2-mi loop boardwalk of Fountain Paint Pot Nature Trail to see fumaroles (steam vents), blue pools, pink mud pots, and mini-geysers in this thermal area. It's popular in both summer and winter because it's right next to Grand Loop Road. Lower Geyster Basin, between Old Faithful and Madison. Easy.

Mud Volcano Interpretive Trail. This ¾-mi round-trip trail loops gently around seething, sulfuric mud pots with such names as Sizzling Basin and Black Dragon's Cauldron and around Mud Volcano itself. 10 mi south of Canyon Village on Grand Loop Rd., Canyon. Easy.

Old Faithful Geyser Loop. Old Faithful and its environs in the Upper Geyser Basin are rich in short-walk options, starting with three connected loops that depart from Old Faithful visitor center. The 0.75-mi loop simply circles the benches around Old Faithful, filled nearly all day long in summer with tourists. Currently erupting approximately every 94 minutes, Yellowstone's most frequently erupting big geyser -- although not its largest or most regular -- reaches heights of 100 to 180 feet, averaging 130 feet. Old Faithful Village, Old Faithful. Easy.

Porcelain Basin Trail. At Norris Geyser Basin, this ¾-mi, partial-boardwalk loop leads from the north end of Norris Museum through whitish geyserite stone and past extremely active Whirligig and other small geysers. Grand Loop Rd., Norris. Easy.

Storm Point Trail. Well marked and mostly flat, this 1 1/2-mi loop leaves the south side of the road for a perfect beginner's hike out to Yellowstone Lake. The trail rounds the western edge of Indian Pond, then passes moose habitat on its way to Yellowstone Lake's Storm Point, named for its frequent afternoon windstorms and crashing waves. Heading west along the shore, you're likely to hear the shrill chirping of yellow-bellied marmots, rodents that grow as long as 2 feet. Also look for ducks, pelicans, and trumpeter swans. You will pass several small beaches where kids can explore on warm summer mornings. 3 mi east of Lake Junction on East Entrance Rd., Fishing Bridge. Easy.

Two Ribbons Trail. This accessible, boardwalked path runs along the Madison River for 1 1/2 mi round-trip. Grand Loop Rd. at Old Gardiner Rd. Easy.

Moderate

Beaver Ponds Loop Trail. The hike to Beaver Ponds is a 2 1/2-hour, 5-mi round-trip starting at Liberty Cap in the busy Lower Terrace of Mammoth Hot Springs. You enter Yellowstone backcountry within minutes as you climb 400 feet through spruce and fir, passing several ponds and dams, as well as a glacier-carved moraine, before emerging on a windswept plain overlooking the 45th parallel (Montana/Wyoming border), Boiling River, and the North Entrance. Look up to see Everts Peak to the east, Bunsen Peak to the south, and Sepulcher Mountain to the west. Bear, elk, bighorn sheep, coyote, and fox may frequent the area. Your final descent into Mammoth Springs offers great views of Mammoth Springs. Grand Loop Rd. at Old Gardiner Rd., Mammoth Hot Springs. Moderate.

Bunsen Peak Trail. Past the entrance to Bunsen Peak Road, the moderately difficult trail is a 4-mi, three-hour round-trip that climbs 1,300 feet to Bunsen Peak for a panoramic view of Blacktail Plateau, Swan Lake Flats, the Gallatin Mountains, and the Yellowstone River valley. (Use a topographical map to find these landmarks.) Grand Loop Rd., 1 1/2 mi south of Mammoth Hot Springs. Moderate.

Mystic Falls Trail. From the Biscuit Basin boardwalk's west end, this trail gently climbs 1 mi (3 1/2 mi round-trip from Biscuit Basin parking area) through heavily burned forest to the lava-rock base of 70-foot Mystic Falls. It then switchbacks up Madison Plateau to a lookout with the park's least-crowded view of Old Faithful and the Upper Geyser Basin. 3 mi north of Old Faithful Village off Grand Loop Rd., Old Faithful. Moderate.

North Rim Trail. Offering great views of the Grand Canyon of the Yellowstone, the 1¾-mi North Rim Trail runs from Inspiration Point to Chittenden Bridge. You can wander along small sections of the trail or combine it with the South Rim Trail. Especially scenic is the 0.5-mi section of the North Rim Trail from the Brink of the Upper Falls parking area to Chittenden Bridge that hugs the rushing Yellowstone River as it approaches the canyon. Portions of this trail may be affected, or closed, by the closure of the North Rim Road for all of 2008, so check with park rangers. 1 mi south of Canyon Village, Canyon. Moderate.

Observation Point Loop. A 2-mi round-trip from the temporary Old Faithful Visitor Center leaves Geyser Hill Loop boardwalk and becomes a trail shortly after the boardwalk crosses the Firehole River; it circles a picturesque overview of Geyser Hill with Old Faithful Inn as a backdrop. You may also see Castle Geyser erupting as well. Even when 1,000-plus people are crowded on the boardwalk to watch Old Faithful, expect to find fewer than a dozen here. Old Faithful Village, Old Faithful. Moderate.

Purple Mountain Trail. Climbing a steady 1,500 feet from start to finish, this 6-mi round-trip trail takes you through lodgepole-pine forest. At the end of the trail catch views of Firehole and Gibbon valleys. ¼ mi north of Madison Junction, on Madison-Norris Rd.

Shoshone Lake-Shoshone Geyser Basin Trail. A 22-mi, 11-hour, moderately difficult overnight trip combines several shorter trails. The trail starts at the DeLacy Creek Trail, gently descending 3 mi to the north shore of Shoshone Lake. On the way, look for sandhill cranes and browsing moose. At the lake turn right and follow the North Shore Trail 8 mi, first along the beach and then through lodgepole-pine forest. Make sure you've reserved one of the several good backcountry campsites (reservations can be made at any ranger station in the park). Take time to explore the Shoshone Geyser Basin, reached by turning left at the fork at the end of the trail and walking about ¼ mi before bedding down for the night. On your second morning, turn right at the fork, follow Shoshone Creek for 2 mi, and make the gradual climb over Grant's Pass. At the 17-mi mark the trail crosses the Firehole River and divides; take a right onto Lone Star Geyser Trail and continue past this geyser through Upper Geyser Basin backcountry to Lone Star Geyser Trailhead. 8 mi east of Old Faithful Village on north side of Grand Loop Rd., Old Faithful. Moderate.

Slough Creek Trail. Starting at Slough Creek Campground, this trail climbs steeply along a historic wagon trail for the first 1 1/2 mi before reaching expansive meadows and prime fishing spots, where moose are common and grizzlies occasionally wander. From this point the trail, now mostly level, meanders another 9 1/2 mi to the park's northern boundary. Anglers absolutely rave about this trail. 7 mi east of Tower-Roosevelt off Northeast Entrance Rd. Moderate.

South Rim Trail. Partly paved and fairly flat, this 4 1/2-mi loop along the south rim of the Grand Canyon of the Yellowstone affords impressive views and photo opportunities of the canyon and falls of the Yellowstone River. It starts at Chittenden Bridge. Along the way you can take a break for a snack or a picnic, but you'll need to sit on the ground, as there are no picnic tables. Beyond Artist Point, the trail crosses a high plateau and meanders through high mountain meadows, where you're likely to see bison grazing. Chittenden Bridge, off South Rim Dr., Canyon. Moderate.

Specimen Creek Trail. Starting at Specimen Creek Trailhead, follow the 2 1/2-mi trail and turn left at the junction; you'll pass petrified trees to your left. At the 6 1/2-mi mark, turn left again at the fork and start climbing 1,400 feet for 2 mi up to Shelf Lake, one of the park's highest bodies of water, at an altitude of 9,200 feet. Stay at one of the pair of designated backcountry campsites, which you can reserve at any ranger station in the park. Just past the lake is the trailhead for Skyline Trail. Watch for bighorn sheep as you approach Bighorn Peak's summit. The trail's most treacherous section is just past the summit, where it drops 2,300 feet in the first 2 1/2 mi of descent; make sure you take a left where the trail forks at the big meadow just past the summit to reach Black Butte Creek Trail. Moose and elk can be seen along this last 2 1/2-mi stretch. U.S. 191, 27 mi north of West Yellowstone. Moderate.

Difficult

Avalanche Peak. On a busy day in summer, maybe six parties will fill out the trail register at the Avalanche Peak trailhead, so you won't have a lot of company on this hike. Yet many say it's one of the best-kept secrets in the park. Starting across from a parking area on the East Entrance Road, the difficult 4-mi, 4-hour round-trip climbs 2,150 feet to the peak's 10,566-foot summit, from which you'll see the rugged Absaroka Mountains running north and south. Some of these peaks have patches of snow year-round. Look around the talus and tundra near the top of Avalanche Peak for alpine wildflowers and butterflies. Don't try this trail before late June or after early September -- it may be covered in deep snow. Also, rangers discourage hikers from attempting this hike in September or October because of bear activity. Whenever you decide to go, carry a jacket: the winds at the top are strong. 2 mi east of Sylvan Lake on north side of East Entrance Rd., Fishing Bridge. Difficult.

Heart Lake-Mt. Sheridan Trail. This very difficult 24-mi, 13-hour round-trip provides one of the park's top overnight backcountry experiences. After traversing 5 1/2 mi of partly burned lodgepole-pine forest, the trail descends into Heart Lake Geyser Basin, reaching Heart Lake at the 8-mi mark. This is one of Yellowstone's most active thermal areas; the biggest geyser here is Rustic Geyser, which erupts to a height of 25 to 30 feet about every 15 minutes. Circle around the northern tip of Heart Lake and camp at one of five designated backcountry sites on the western shore (remember to get your permit beforehand). Leave all but the essentials here as you take on the 3-mi, 2,700-foot climb to the top of 10,308-foot Mt. Sheridan. To the south, if you look carefully, you can see the Tetons. 1 mi north of Lewis Lake on east side of South Entrance Rd., Grant Village. Difficult.

Osprey Falls Trail,The 4-mi, two-hour round-trip starts near the entrance to Bunsen Peak Road. A series of switchbacks drops 800 feet to the bottom of Sheepeater Canyon and the base of the Gardner River's 151-foot Osprey Falls. As at Tower Fall, the canyon walls are basalt columns formed by ancient lava flow. Bunsen Peak Rd., 3 mi south of Mammoth Hot Springs. Difficult.