Aspen, CO: Four Pass Loop

Like peaks, lakes, and wildflowers? You’ll love this Rockies classic.

Backpacker editors just named the Four Pass Loop one of our favorite trips ever—and Rockies readers agree, voting this their #1 hike. Here’s their advice for getting the 26-mile, four-day route’s sparkling creeks, peak-ringed lakes, and, yes, a quartet of 12,000-foot passes all to yourself.

Go counterclockwise, starting at Maroon Lake, where the purple-streaked Maroon Bells dominate the sky. Follow the north shore on the West Maroon Trail, then turn right at the signed junction. Switchback .2 mile to Crater Lake and a showstopping photo op of the Bells. Continue on West Maroon Trail 3.7 miles, then choose one of the established campsites edging the meadow. (Resist the urge to press on—the next campsite isn’t for five miles.)

On day two, continue uphill, gaining 800 feet in .9 mile as you inch toward 12,480-foot West Maroon Pass, perched between the Mars-like rock of Belleview Mountain and Mt. Bellview. The trail then descends into Hasley Basin, where you’ll hike past meadows of Indian paintbrush and columbine (peak flowers: late July) before turning right at a junction. Turn right again at a three-way junction and gain 400 feet to the crest of 12,415-foot Frigid Air Pass. From here, drop into lush Fravert Basin before reentering a conifer forest. Continue west for 1.3 miles to your second campsite, one of several spots scattered among ponderosas 150 feet from the North Fork of the Crystal River.

Next morning, you’ll ford the 20-foot-wide creek. At mile 13.7, turn right and switchback steeply through aspen groves en route to pass #3: 12,400-foot Trail Rider Pass, just below Snowmass Peak. Drop to Snowmass Lake, your next camp. On your final day, turn right at the junction and hike beneath sheer, red-rock cliffs and across Snowmass Creek before powering up to 12,462-foot Buckskin Pass. Look for mountain goats at mile 21.5; you can often spot nannies with kids in summer. Rejoin the West Maroon Trail to finish the loop.

Maps: USGS Maroon Bells and Snowmass Mountain ($8,

Permit: Register at trailhead; (970) 925-3445

Gear up: Ute Mountaineer, 308 S. Mill St., Aspen, CO; (970) 925-2849

-Mapped by Kristy Holland

Trail Facts

  • Distance: 41.9



Location: 39.099651, -106.937668

The trailhead parking lot is equipped with toilets and drinking fountains. Though there are three lots, they may fill on peak weekends and even overnight visitors might have to take the shuttle bus from the Aspen Highlands Village at the base of Maroon Creek Road.


Location: 39.098534, -106.940826

Follow Crater Lake Trail signs through the parking area and along the north shore of Maroon Lake. Be sure to stop for photos at this picturesque spot.


Location: 39.098091, -106.94603

Turn right at the signed Y-junction, and head uphill toward Crater Lake.


Location: 39.097122, -106.947838

The trail crosses two plank bridges just before a self-registration kiosk at the wilderness area boundary. Overnight hikers are required to fill out the free registration tag and leave detailed plans.


Location: 39.091442, -106.958328

The trail opens up after a few short switchbacks and begins a level, 0.3-mile wind through lichen-covered piles of angular rock. Up ahead you'll catch a glimpse of Crater Lake's muddy waters on the left.


Location: 39.088654, -106.965958

Turn left at this trail junction to follow the West Maroon Trail #1970. If you had a late start from the trailhead, you may choose to stop for the night at one of several Crater Lake campsites (site 6 is a favorite). If you're prepared for a longer hike, continue left up the valley toward West Maroon Pass.


Location: 39.08429, -106.969894

A split-log bridge precedes this ponderosa-shaded clearing. Pass left-hand spur trails to Crater Lake's Campsites 7-9 and 10-11 up ahead.


Location: 39.078888, -106.971786

The trail winds atop a rockfall and scree field. Northern views of Crater Lake are a little distracting, but the well-trod trail is easy to follow.


Location: 39.065048, -106.971903

Water levels may be low in late summer, but this first substantial river crossing at mile 3.5 might be a snowmelt-swollen challenge in early summer. On the river's east side, a rocky clearing is a good spot to stop and have a snack and wring out your socks.


Location: 39.055191, -106.976898

Several user-created trails merge on the opposite side of this 10-foot stream crossing. In late summer you may be able to stay dry, but expect to get wet when the river is swollen in early spring.


Location: 39.042486, -106.986365

There are no designated campsites above Crater Lake, but camping is allowed. Use established sites (there are 2-3 sites around the edges of this meadow) to reduce impact along this heavily-used trail.


Location: 39.036419, -106.997261

After rolling uphill and across some easy stream crossings, the climb intensifies as the vegetation and air thins near the pass. Alpine meadows and flowers give way to red-tinted rocks for the final few hundred feet of climbing.


Location: 39.035732, -106.997307

West Maroon Pass, a 12,480-foot shoulder between Mount Bellview to the south and Belleview Mountain to the north, offers spectacular views of the valleys on either side.


Location: 39.038279, -107.008702

Turn right at this signed Y-junction toward Frigid Air Pass. The trail climbs gently to the northwest.


Location: 39.042725, -107.010805

There are no adequate campsites on this steep, hillside. Plan to spend your first night on the east side of West Maroon Pass, or allow plenty of time for a very long day one (over Frigid Air into Fravert Basin).


Location: 39.052194, -107.023779

Hang a right at the signed 3-way junction. You'll traverse a grassy bowl beneath Frigid Air Pass before turning sharply uphill.


Location: 39.053846, -107.020398

This short, but very steep and loose 400 foot climb ends at the 12,415-foot pass. Welcome views of the Fravert Basin's grassy expanse and the Maroon Bells' rugged backsides await.


Location: 39.06726, -107.016007

The trail drops through shrubby alpine meadows and enters the woods for the first time in 5 miles. As the trail enters the woods it passes a few small, slanted campsites.


Location: 39.077617, -107.019029

The trail crosses several drainages as it winds down the basin's upper half.


Location: 39.081462, -107.025587

This shady campsite is large enough for several tents, but within a few hundred yards along the trail there are other, smaller sites as well.


Location: 39.081344, -107.027962

This ledge offers spectacular views into the basin's lower half. You'll catch glimpses of a waterfall on your right before the trail turns sharply downhill over several switchbacks.


Location: 39.082489, -107.041329

A Halsey Basin trail and westbound user trails merge at an unmarked junction in a clearing near a large, fallen tree. Continue straight toward the next junction before turning right, or turn right here to follow the faint user-trail toward the river.


Location: 39.082607, -107.042244

This shaded campsite sits near a creek and is less than 150 yards away from the North Fork Crystal River crossing.


Location: 39.083748, -107.041975

The trail's most substantial river crossing is a wet 20-foot wade across the North Fork Crystal River at mile 11. Consider bringing trekking poles for this section of the trip.


Location: 39.088512, -107.05574

Turn right at the Y-junction toward Trailrider Pass. The next 1.5 miles zigzag up a steep, aspen-dotted hillside.


Location: 39.096933, -107.062464

Turn right at this Y-junction and continue following signs north and east toward Trail Rider Pass. Another set of trails leads west toward Geneva Lake.


Location: 39.098566, -107.052218

There is a small lake, a few lumpy campsites, and a small stream in this alpine valley below Trail Rider Pass.


Location: 39.105086, -107.04904

A few short, steep switchbacks top out at 12,400-foot Trail Rider Pass. Snowmass Peak looms to the north and the trail shoots left and switchbacks downhill toward Snowmass Lake.


Location: 39.113211, -107.034163

On a steep hillside just above Snowmass Lake, the trail winds around and across several scree fields. You'll have to rock hop on a few short sections of trail.


Location: 39.116675, -107.02836

Continue straight at this 3-way junction to head toward Buckskin Pass. Optional: turn left for a 10-minute detour to an open picnic-worthy clearing near the lakeshore.


Location: 39.117432, -107.030106

This clearing offers great views of Snowmass Mountain looming above the lake's western shore. There are several campsites in the forest just east of here.


Location: 39.117172, -107.02636

Go straight at 3-way junction to continue toward Buckskin Pass. Or, turn left to scope out several individual campsites and a larger group site, too.


Location: 39.108967, -107.016304

This rocky outcropping hides another campsite, just 100 feet to the left of the trail. Sites like this one, away from the lake, are likely to be less crowded during peak summer weekends.


Location: 39.107479, -107.008934

After passing beneath a red-hued rock face, the trail traverses a meadow over a series of steep, loose, rocky switchbacks.


Location: 39.105953, -107.004135

The trail crisscrosses Snowmass Creek near the east side of this marshy wetland area. The trail turns uphill for its final pass-bound climb.


Location: 39.102016, -106.992546

At mile 21.5 the trail hits 12,462-foot Buskskin Pass before turning downhill toward the trailhead (the route's high point). Snowmass Mountain dominates the western view and grassy slopes nearby offer dramatic contrast. Watch for mountain goats that frequent the rocky outcroppings above the pass.


Location: 39.100254, -106.98497

Stay straight at the 3-way junction continuing downhill and bypassing the Willow Pass and Willow Lake Trail.


Location: 39.093544, -106.9786

A shallow 20-foot stream crossing here may present trouble when water levels are high, but a wide section of relatively flat, pine-covered trail crosses several small streams up ahead.


Location: 39.090641, -106.977905

Stop at this rocky outcropping for a peek into Minnehaha Gulch. Be careful near the cliff edge, the log-jammed river is about 100 feet below the rocky cliff.


Location: 39.08902, -106.969559

A stretch of broken aspen is evidence of this area's winter avalanche danger.


Location: 39.088654, -106.965958

Continue straight at this 3-way junction to close this route's 23-mile loop. It's an easy, rolling 1.7 miles downhill toward the trailhead.

Below Trail Rider

Location: 39.100218, -107.049714

The valley and alpine lake on the west side of Trail Rider Pass.


Location: 39.090359, -107.057535

The hillside path toward Trailrider Pass switchbacks through small groves of aspen.

Basin Views

Location: 39.081207, -107.0278

A northwest view of the North Fork Crystal River's basin near mile 11.6.


Location: 39.099027, -106.984563

If you need a mid-downhill rest, stop at this trail-side cascade. It's just below treeline and has a few flat-topped rocks perfect for sitting on.

Fravert Basin

Location: 39.083472, -107.041699

Looking back toward Fravert Basin at a riverside junction just before the North Fork Crystal River crossing.

Fravert Basin

Location: 39.053785, -107.020097

A view of the Fravert Basin from Frigid Air Pass.


Location: 39.052118, -107.023959

Frigid Air Pass is just a short, steep climb above this trail sign at mile 8.5.

Maroon Bells

Location: 39.098228, -106.942077

A view of the Maroon Bells from the trailhead.

Pass Climb

Location: 39.036853, -106.997309

A hiker climbs the rocky, open trail toward West Maroon Pass.

Trail Rider Pass

Location: 39.105022, -107.048936

The view of Snowmass Lake from Trail Rider Pass.

Stream Crossing

Location: 39.065115, -106.971302

Even though this late-summer stream crossing is dry and easy, use caution on slick rocks.


Location: 39.045119, -106.985421

Summer wildflowers decorate already spectacular views of the 13,000-foot bowl above West Maroon Creek.

Trail 1970

Location: 39.088502, -106.966109

West Maroon Trail #1970 turns south toward Crater Lake.

Trailhead Bus Stop

Location: 39.098494, -106.940274

A shuttle service stops at the trailhead and maybe the access only option for peak-season hikers.

Trail Rider View

Location: 39.104955, -107.048979

The southwestern view from Trail Rider Pass.

West Maroon Pass

Location: 39.042453, -106.986108

A picturesque campsite below West Maroon Pass.