Chasm Lake

Chasm Lake sits in a granite bowl directly under the Diamond, the 1,000-foot east face of Longs Peak, and the trail to it is the best day hike in Rocky Mountain National Park for people who want to see the big mountain up close without climbing it. It shares the first 3.5 miles with the Longs Peak Keyhole Route, then leaves the crowd at Chasm Junction for a ledge traverse and a scramble to the lake at 11,760 feet. The round trip is 8.4 miles with 2,360 feet of gain.

From the Longs Peak trailhead, the East Longs Peak trail climbs through lodgepole and spruce past the Goblins Forest campsites, crosses Alpine Brook on a footbridge, and switchbacks up through the last of the trees. Above treeline it crosses open tundra with Longs and Mount Meeker filling the sky, and reaches Chasm Junction at about 3.5 miles, where the Keyhole Route goes right toward Granite Pass.

Take the left fork. The Chasm Lake trail contours across a steep slope above Peacock Pool and Columbine Falls, with a stream crossing on the ledge that is icy early and late in the season, and reaches the meadow and the stone patrol cabin below the lake. The last quarter mile is a cairned scramble up a rock band, Class 2, to the lip of the bowl and Chasm Lake, with the Diamond rising 1,000 feet straight out of the far shore. Return the same way.

The Longs Peak trailhead is 9 miles south of Estes Park on Colorado 7 at the Longs Peak Ranger Station. The lot holds about 70 cars and is full by 3 AM on summer weekends with Keyhole climbers, so Chasm Lake hikers either arrive in the dark or park along the highway where it is allowed, which adds a mile. The park entrance fee applies and there is no fee station here; buy the pass online. The timed-entry permit applies only for entry between 9 AM and 2 PM in season, which is after most people have started. Toilets at the trailhead.

No dogs anywhere in the park. The distance, the altitude, and the scramble at the end make it a trail for older kids who hike. Carry three liters; the water on the tundra needs a filter. The trailhead is at 9,400 feet and the lake is above 11,700; people arriving from low elevation should sleep a night in Estes Park first. The Longs Peak Keyhole guide covers the climb beyond the junction, the Longs Peak weather guide covers the storm timing, and the RMNP region page has the permit details.