Lost Lake is one of the most popular hiking destinations on Colorado's Front Range, reached by a 4.2-mile round-trip trail from the Hessie Trailhead near the old mining town of Eldora in Boulder County. The path climbs 830 feet through mixed conifer and aspen forest, crosses several small streams, passes a striking waterfall, and ends at an alpine lake surrounded by the peaks of the Indian Peaks Wilderness. On a clear day, the combination of still water, dark spruce, and rocky summits above treeline feels more like the Swiss Alps than a spot just over an hour from Denver.
The trail begins on a wide old mining road before narrowing into singletrack that winds uphill through shaded forest. About halfway to the lake you will encounter a waterfall worth pausing for, and the final stretch opens into subalpine meadows before the lake comes into view. The hike is rated moderate and is doable for fit families with children, though the rocky, root-crossed terrain demands sturdy footwear. After snow, the upper sections become slippery and traction devices are recommended. Most hikers complete the round trip in about two hours, leaving plenty of time to explore the shoreline trail that circles much of the lake.
Lost Lake sits just outside the Indian Peaks Wilderness boundary at an elevation near 9,850 feet. Eight designated primitive campsites surround the lake on a first-come, first-served basis, making it a popular overnight destination for backpackers who want a mountain-lake camp without a long approach. Fishing is permitted with a valid Colorado fishing license, and the lake holds brook trout and rainbow trout that provide quiet action for anglers willing to pack in a rod.
Access is the main logistical challenge. The Hessie Trailhead has fewer than five parking spots, and the approach road is unpaved and narrow. On summer weekends and holidays, Boulder County runs a free shuttle from Nederland that departs every 15 to 20 minutes, making the shuttle by far the easiest way to reach the trail. Dogs are welcome and the trail sees plenty of four-legged hikers.
Fall is arguably the best season here, when the aspen groves along the lower trail blaze gold and the summer crowds thin. Winter visits are possible but require snowshoes or microspikes, and the trail can be harder to follow under snow. Spring brings muddy conditions and lingering snowpack at higher elevations, so late June through early October is the prime window.
Lost Lake rewards every season and every skill level. It is close enough to Boulder and Denver for a half-day outing, scenic enough to feel like real wilderness, and varied enough to bring you back more than once.