Boulder, CO: Rainbow Lakes to Arapahoe Glacier

One of the most eye-popping routes in Boulder County, this 13-mile out-and-back through burly Indian Peaks Wilderness offers a bit of everything Front Range: mountain-rimmed lakes, fields of low bush, aspen groves, coniferous forest, a hidden waterfall, and far-reaching, 360-degree views of Rocky Mountain paradise.

Although the trip starts off nice and easy along Rainbow Lakes, the climb to Arapahoe Glacier Lookout gains more than 3,600 feet over exposed, rocky terrain. The first half of the Arapahoe Glacier Trail is a 3-mile steady ascent under a pine and spruce canopy. Once past the tree cover, marvel at the massive lakes (Goose, Island, and Silver) that stretch from the Continental Divide to Arapahoe Moraine. Look right for views of Bald, Klondike, and Chittenden Mountains.

Follow the thin trail as it switchbacks to a 12,000-foot saddle where vast mountain views await. From the saddle, it’s a 2-mile march over gnarly singletrack to Arapahoe Glacier Lookout. Even if you take time to catch your breath at the lookout, you’ll lose it again at the sight of craggy North and South Arapahoe peaks. When finished, retrace your steps back to the trailhead.

-Mapped by MacKenzie Ryan and Chelise Simmons

Trail Facts

• Distance: 21.1

Waypoints

RLA001

Location: 40.010495, -105.572214

Rainbow Lakes Trailhead: Follow the soft, dirt trail west. A dried-up river bed will be on the right.

RLA002

Location: 40.011043, -105.573836

Reach the Indian Peaks Wilderness Boundary and turn left up the rocky trail toward Rainbow Lakes.

RLA003

Location: 40.012003, -105.577455

Pass the first of three lakes on the left. A spur trail is clearly visible to the left of the Rainbow Lakes Trail.

RLA004

Location: 40.013, -105.583259

Pass a marshy field full of low bushes on the left-hand side of the trail. Continue along the trail, and cross over two creeks on wooden footbridges. There is some boulder-hopping involved during the summer season.

RLA005

Location: 40.012776, -105.584933

Reach the last two Rainbow Lakes, which sit at the eastern base of Caribou Peak. A spur trail to the left takes hikers down to the first lake. To access the second lake from the trail, scramble up the boulder field. A smaller lake sits south of the massive rock pile. Turn around and retrace steps back to the trailhead.

RLA006

Location: 40.010479, -105.57224

After reaching the Rainbow Lakes Trailhead, continue left through the parking lot toward the Glacier Rim Trailhead.

RLA007

Location: 40.010716, -105.571608

Reach the Glacier Rim Trailhead and bear right up the Glacier Rim Trail.

RLA008

Location: 40.016936, -105.570943

On the right side of the trail, a break in the trees reveals a sweeping panorama of Boulder County and the surrounding mountains.

RLA009

Location: 40.023283, -105.586486

After a short switchback ascent, the trail begins to climb up a steep grade.

RLA010

Location: 40.022973, -105.592894

After hiking a few miles through pine and spruce cover, the trail reaches wide open space. From here, the thin, crushed granite singletrack travels west toward a series of long switchbacks.

RLA011

Location: 40.022995, -105.597496

Goose and Silver lakes are to the right. Continue east for a short distance, then turn up the mountain.

RLA012

Location: 40.014494, -105.614152

After following the switchbacks along the north face of the first mountain, reach a saddle with 360-degree views. West of this point, the Continental Divide stretches north to south. Eldora Ski Resort and Bald Mountain are directly south. Boulder and Denver are to the far east. After marveling at the scene, follow the ridgeline trail over a rocky, crushed granite trail.

RLA013

Location: 40.015816, -105.643995

Arapahoe Glacier Lookout: The Arapahoe Peaks form a bowl to the left. To continue further, bear left and continue 3 miles to Arapahoe Pass. To turn back, retrace steps back to Glacier Rim Trailhead.

Rainbow Lakes Trailhead

Location: 40.010502, -105.57216

©MacKenzie Ryan

First Lake

Location: 40.010097, -105.579042

©MacKenzie Ryan

Field of Low Bush

Location: 40.013088, -105.582733

©MacKenzie Ryan

Second Lake

Location: 40.012768, -105.584664

©MacKenzie Ryan

Third Lake

Location: 40.012768, -105.584857

©MacKenzie Ryan

Glacier Rim Trailhead

Location: 40.010721, -105.571522

©MacKenzie Ryan

Boulder County and the surrounding mountains

Location: 40.016112, -105.570631

©MacKenzie Ryan

Fallen Trees

Location: 40.021896, -105.582561

©MacKenzie Ryan

Views to the South

Location: 40.021173, -105.579901

©MacKenzie Ryan

Breaking through the tree cover

Location: 40.022751, -105.585737

©MacKenzie Ryan

Above Treeline

Location: 40.022619, -105.590887

©MacKenzie Ryan

Island and Silver Lakes

Location: 40.022751, -105.589514

©MacKenzie Ryan

Goose Lake

Location: 40.018281, -105.606165

©MacKenzie Ryan

The Trail

Location: 40.022718, -105.596466

©MacKenzie Ryan

The Saddle

Location: 40.015027, -105.613332

©MacKenzie Ryan

Eagle soaring past the saddle

Location: 40.014074, -105.627279

©MacKenzie Ryan

En route to the lookout

Location: 40.013154, -105.637429

©MacKenzie Ryan

Easternmost mountain at Arapahoe Glacier Lookout

Location: 40.014468, -105.641613

©MacKenzie Ryan

North Arapahoe Peak

Location: 40.015192, -105.643158

©MacKenzie Ryan

South Arapahoe Peak

Location: 40.014797, -105.642386

©MacKenzie Ryan