Length: 8.4 miles round-trip and 1,700 vertical feet
Difficulty: Most difficult
Why We Love It: Blue glacial ice is a magical (and increasingly rare) sight.
Pre-hike Buzz: Try Nederland’s New Moon Cafe for a cup of coffee or chai and a bagel with bacon, eggs, or butter.
When To Go: July through September, when the trail is free of snow
Restrooms: Vault toilets at trailhead
Distance from Denver: About 50 miles
Dogs: Must be on a hand-held leash
Brainard Lake Recreation Area, one of Colorado’s most popular (and most accessible) mountain gateways, has a number of deservedly popular destinations, including Mt. Audubon, Mitchell Lake, and sparkling Lake Isabelle. But not many visitors realize that Lake Isabelle is halfway to an even more spectacular sight: one of Colorado’s 14 remaining glaciers (and one of only seven larger than 0.1 square kilometers). Of these larger ice patches, Isabelle Glacier is by far the easiest to get to, owing both to Brainard Lake’s paved access road and the well-built trail leading up to the glacier’s rough edge.
Beginning at the Long Lake trailhead, follow the Pawnee Pass Trail through the forest to Lake Isabelle, where you’ll be treated to gorgeous view of Navajo Peak, a craggy thirteener. Instead of turning right to ascend Pawnee Pass, continue straight to head west along the signed Isabelle Glacier Trail. The path crosses some rocks before contouring around the north side of the lake.
Once around the shoreline, you leave the trees behind as the trail ascends through fields of Colorado columbine and other colorful wildflowers, rumbling cascades, sheer cliffs, and increasingly closer views of Navajo Peak. Continue to a flat, marshy area where you’ll need to rock-hop across a small creek and then up a steep pitch before arriving at a small alpine lake deep in a glacial canyon. From here the trail follows a series of switchbacks past a waterfall and up the canyon’s northern side to a loose, bouldery slope, which is the edge of the pile of rocks and sediment (the glacial moraine) that the glacier dropped here. You’ll know you’ve reached the end when the view down to the impressive patch of snow and ice opens up.
For the best view of the dramatic cirque—a bowl-shaped depression formed by erosion—hop up on one of the higher boulders. It’s a great spot to make a snowperson (even in August!) or to enjoy a picnic while glancing down at the brilliant turquoise lake deep in the cirque, where meltwater pools, as well as to see the glacial ice, which looks blue because the ice crystals scatter the short wavelengths of the incoming light.
Getting there: To reach the Brainard Lake Recreational Area, follow US-36 west to the Canyon Boulevard exit in Boulder. Exit here and follow Canyon (CO-119) for about 16 miles up Boulder Canyon to Nederland. At the town’s first (and only) traffic circle, follow the sign to CO-72 (the Peak-to-Peak Highway). Continue north along the Peak-to-Peak about 11.5 miles, then take a sharp left turn onto the signed Brainard Lake Road. After paying the fee ($12) at the Brainard Lake Recreation Area entrance booth, continue along this road to the Long Lake trailhead.