Overview
Lost Lake sits in the central portion of the Rawah Wilderness in the northern Colorado section of Medicine Bow-Routt National Forests. The 6.0-mile loop provides a shorter Rawah Wilderness experience than the full lakes loop, visiting two or three named lakes and crossing an open meadow section with views of the surrounding ridge terrain. The Rawah Wilderness was designated in 1964 and covers approximately 73,000 acres of the northern Colorado mountains along the Wyoming border, making it one of the oldest wilderness designations in the state.
The lake basins here sit between 10,000 and 11,000 feet, and the terrain combines dense spruce and fir forest on the lower approach with open rocky meadows and tundra near the lakes. The Continental Divide Trail passes through the general Rawah corridor, and the area sees both day hikers and backpackers, though the numbers are modest by Colorado standards.
This is the best single-day introduction to the Rawah Wilderness for hikers who want genuine wilderness feel without committing to a multi-day backpack.
The Route
Miles 0.0 to 1.5: Trailhead to Wilderness Entry
The trail climbs from the FR-517 trailhead through lodgepole and subalpine forest into the wilderness. The grade is steady but manageable, with good tread through the lower forest section. The wilderness boundary sign marks the entry point at approximately 1.5 miles. From here, motorized and mechanized equipment are prohibited, and the trail feels noticeably more remote.
Miles 1.5 to 3.5: Lake Basin Traverse
The loop enters the lake basin area, passing smaller tarns before reaching Lost Lake at mile 2.5. The tarns are shallow and sometimes partially surrounded by bog, so staying on the maintained tread is important for both soil protection and dry feet. Open meadow sections between the lakes provide views of the surrounding ridge and the high points of the Rawah range. Native cutthroat trout are present in Lost Lake and in the larger unnamed tarns; fishing is permitted in the wilderness (Colorado license required as of 2026).
Miles 3.5 to 6.0: Loop Return
The loop returns via a different drainage back to the trailhead, descending through a slightly different forest character with more mature timber and deeper shade. The two different segments of the loop give the route variety that an out-and-back cannot match. The return section is generally less traveled than the outbound route, so solitude is more likely here.
When to Hike
Mid-July through September for accessible conditions. The lake basin may hold snow and ice into early July, and the approach trail can be muddy through early summer snowmelt. A mid-July first visit is a reasonable baseline.
September for fall color, solitude, and the best chance of stable weather. The aspen and willow near the lake shores turn gold and orange through the first half of September. Afternoon storms become less frequent and less severe than in July and August, though they remain possible. Come prepared for cold temperatures, particularly on the open ridge sections.
What to Bring
Many hikers carry 2 liters of water. The lakes and streams throughout the loop provide filterable water if more is needed, but a filter or treatment tablets are required. Layers for the meadow sections where wind can be significant, particularly on the ridge sections between drainages. Waterproof footwear is worth considering in early season when the trail through bog sections is likely wet.
Trailhead Access
FR-517 in the Rawah Wilderness corridor, Larimer County, Colorado. The forest road conditions can be rough in early season; check current road conditions before driving. No fee to park or hike (as of 2026). Vault toilet at the trailhead. The closest towns for supplies are Walden (to the north) and Fort Collins (to the south via Cache la Poudre Canyon).
Nearby
Rawah Wilderness Lakes Loop extends this experience into a full multi-day wilderness backpack, visiting more of the Rawah lake country in a longer circuit. Medicine Bow Peak Trail in the Wyoming unit provides a summit option in the same combined forest for those interested in the higher terrain of the range.
Check conditions at checking conditions before you go. Practice Leave No Trace principles, camping 200 feet from lake shores in accordance with wilderness regulations.