To reach the Flattop Mountain Trail, first ascend above Bear Lake heading north through young aspen to where the-the Bear Lake TH to Fern Lake TH trail splits from the Bear Lake - Mill Creek Trail. From here, the Flattop Mountain Trail itself begins, leaving to the west along a ridgeline. Soon the Fern - Odessa Lake Trail branches off to the right (northwest) but instead, continue left on the Flattop Mountain Trail, switchbacking steeply uphill. Surmount the forested eastern flank of Flattop pausing for views of Dream Lake, Longs Peak, Emerald Lake and Tyndall Glacier. Tyndall is one of only five active glaciers in the Park and is responsible for carving the valley below.
After treeline, the grades moderate and the switchbacks end. Follow the well-defined path into open tundra, using cairns for guidance over snowfields. The trail reaches a hitching post affording good views of Hallett Peak across the gorge. Next, scale a permanent snowfield and cover level ground on the final approach up to Flattop Mountain. No sign marks the summit, but the Flattop Mountain Trail - Tonohutu Creek Trail junction is generally recognized as your final destination.
This wide flat saddle along the Continental Divide offers a rare opportunity to explore the tundra. See if you can identify landmarks such as Hallett Peak, Otis Peak, Taylor Peak, Longs Peak, Notchtop Mountain, Ptarmigan Point and portions of the Mummy Range, Never Summer Range and Grand Lake.