Chasm Lake

Chasm Lake is a stunning alpine lake at roughly 11,800 feet in Boulder County, nestled directly beneath the sheer east face of Longs Peak inside Rocky Mountain National Park. The Diamond, a 900-foot granite wall rising straight out of the ground above the lake, draws rock climbers from around the world, while the hike to reach the lake rewards every visitor with waterfalls, wildflowers, and one of the most dramatic mountain backdrops in Colorado. Most hikers describe Chasm Lake as one of the finest trails in all of Rocky Mountain National Park, and the moment you scramble over the final ridge to see turquoise water framed by towering rock walls feels genuinely cinematic.

The hiking trail to Chasm Lake is an out-and-back route covering roughly 8.5 to 10 miles round trip with about 2,000 to 2,500 feet of elevation gain. The first two miles pass through alpine forest with lush evergreens, mossy terrain, and babbling brooks. The trail then breaks above treeline into exposed tundra with sweeping views of Mount Meeker, Longs Peak, and Mount Lady Washington. The final half mile involves a rock scramble up boulders to reach the lake basin. Two vault toilets are available along the trail above treeline, which is a welcome surprise at this elevation. Hikers should expect the full trip to take five to seven hours including breaks.

Seasonal conditions at Chasm Lake vary dramatically. Summer brings wildflowers along the lower trail and relatively manageable conditions, though afternoon thunderstorms roll in fast and can be dangerous on the exposed upper sections. Starting before sunrise is strongly recommended to avoid lightning and to catch the spectacular way morning light hits the granite walls. Fall delivers stunning foliage on the lower trail and thinner crowds. Winter and early spring transform the hike into a mountaineering challenge with deep snow, blizzard-like conditions, and icy rock scrambles requiring spikes or crampons. Several hikers report the winter experience as deeply rewarding but suitable only for those with mountaineering experience.

The parking lot at the Longs Peak trailhead fills before 8 a.m. on summer mornings, and latecomers may need to park up to half a mile down the road. No pets are allowed on the trail. The water temperature hovers around 40 degrees Fahrenheit even in summer, and a few adventurous visitors do take a polar plunge. Warm layers, gloves, a hat, and proper hiking boots are essential regardless of season since wind at the lake can be fierce and temperatures drop sharply above treeline. This trail serves as excellent preparation for anyone training for Colorado fourteeners, and many consider it the next best thing to summiting Longs Peak itself.