Fern Lake Trail to Flat Top Mountain Loop

HARD 4 reviews
#154 of 209 trails in

Fern Lake Trail to Flat Top Mountain Loop is a 23.3 mile moderately trafficked loop trail located near Estes Park, Colorado that features a lake and is rated as difficult. The trail is primarily used for hiking, nature trips, and backpacking.

Distance: 23.3 miles Elevation Gain: 5,797 feet Route Type: Loop



nature trips






wild flowers




washed out

no dogs

An excellent single day endurance hike. Get to the trail-head early as there is limited parking. Fern Lake trail goes through several changes from along a fishing creek, to a nice waterfall, and some serious incline grade. Follow Fern Lake Trail for approximately 8.1 miles to Flat Top Mountain Trail for an elevation gain of 1,833'. On the way you will have the opportunity to visit 4 alpine lakes (more mileage, but minimal). Turn to the right on to Flat Top Mountain Trail for 3.4 miles and another 2,341' in elevation gain to tree-line and eventually to Flat Top at 12,329'. For the extra adventure and leg burn Hallett Peak is another 0.6 miles and another 384' up (& down). From Flat Top follow your steps back toward Bear Lake for 4.1 miles and bear to the left towards Bierstadt Lake. After another 2.7 miles you will head toward the Mill Creek CG (NOT the UPPER Mill Creek CG). There's a surprise incline for almost 1 mile around the 20 mile mark (the endurance part). You will enter a burn area and turn left on to Cub Lake Trail towards "The Pool"!.That brings you back to the Fern Lake Trail for the final 1.75 miles to the Trail Head!

5 months ago

I lost a black and white patterned Chaco sandal on this trail on 7/14, near the Fern Falls switchback! If you come upon it, please return it to any visitor’s center within the park!

Thu Sep 20 2018

A great 1 day endurance hike. I pieced this particular hike together to include my favorite hiking objectives; RMNP, loop hikes, getting above tree-line, waterfalls, alpine lakes, mileage and great views in 1 hike! For more details read my description on the trail main page!