Flattop Mountain is accessed from Bear Lake Trailhead in Rocky Mountain National Park. Built in 1925, and rehabilitated in 1940 with Civilian Conservation Corps labor, it is listed on the National Register of Historic Places.
- Trailhead: Bear Lake
- Round trip: 8.6 miles / 13.8 km
- Elevation: 9,475′-12,332′ (+2857′) / 2,888m-3,759m (+871m)
From the trailhead immediately make a right turn onto the Bear Lake Loop Trail. After a short walk along the eastern shore of Bear Lake, make another right turn at the next junction. From here the trail ascends the slopes of the Bierstadt Moraine.
About .5 miles from the trailhead you’ll reach the Bierstadt Lake and Mill Creek Basin junction. Turn left and continue towards Flattop Mountain. The route turns west as it climbs higher and you’ll enjoy spectacular views of Longs Peak, the Keyboard of the Winds, Pagoda Peak and Chiefs Head Peak towards the south. At just over 1 mile from the trailhead you will arrive at the Flattop Mountain Trail junction, which forks off to the left and begins ascending the eastern slopes of the mountain.
Once on the Flattop Mountain trail, the climb becomes steeper for the rest of the route. About 1.5 miles from the trailhead (~10,500 feet) you will reach the Dream Lake Overlook. Once leaving the Dream Lake overlook it’s a short hike to tree-line. Looking towards the east are views of Bierstadt Lake, Sprague Lake and much of the Glacier Basin area.
After about 3 miles from the trailhead you’ll reach the Emerald Lake Overlook. This scenic overlook rises more than 1,200′ above Emerald Lake. Continue on for less than a mile and you will be just below the summit of Flattop Mountain where there is a horse hitch. The slope begins to become more gradual and eventually leveling out. The end of the Flattop Mountain Trail is at the junction with the North Inlet Trail and Tonahutu Creek Trail. Although there are no signs indicating that you’re at the top, this is the unofficial summit of Flattop Mountain.
The first ascent is unrecorded, as Ute and Arapahoe Indians used a trail over Flattop to cross the Continental Divide for hundreds of years.