Three Island Lake

Managing agency

Arapaho-Roosevelt NF — Boulder RD

Three Island Lake is an 11.4-mile out-and-back trail located in Colorado near the Arapaho-Roosevelt National Forest, Boulder Ranger District. The trail offers access to an alpine lake surrounded by mountain scenery typical of the Front Range. This moderate-distance hike is ideal for day hikers seeking a substantial workout with clear turnaround point. The out-and-back format allows hikers to set their own pace and distance, making it accessible for various fitness levels. Hikers can choose to hike the full 11.4 miles or turn around earlier if desired. The trail is managed by the Arapaho-Roosevelt National Forest Boulder Ranger District, ensuring maintained conditions and adherence to Forest Service regulations. The destination lake itself provides a scenic alpine environment for rest and exploration once you've completed the approach. The trail gains elevation as it climbs toward the lake, providing a cardiovascular challenge typical of Colorado's higher-elevation hikes. Plan for a full day of hiking to complete the full distance at a comfortable pace, and bring adequate water and supplies for the journey.