Willis Lake (11,742') is located 5.15 miles from Willis Gulch Trailhead in the San Isabel National Forest. It lies in a deep, tightly hemmed basin capped by Mount Hope (13,933'), Ervin Peak (13,531'), Mt Blaurock (13,616') and Rinker Peak (13,302').

There's no clear path off the main trail to Willis Lake, but once down it's fairly easy to walk around the entire shore

The trail rises up the west valley wall and above the lake to avoid thick willow and large boulders that choke the valley floor

Mount Blaurock (13,616') and Ervin Peak (13,531') form the valley headwall, named after William Ervin and Carl Blaurock who were climbing pioneers in the early 1900s

The trail passes a large pond in a wide, flat section of the valley between Mount Hope and Rinker Peak about 1/2 mile before reaching the lake

Willis Lake is uniquely long, narrow and almost fully enclosed by valley walls and a moraine-like barrier on its outlet

After a strenuous push up a narrow gulch, the trail emerges in the upper valley and crosses a tedious scree field

Willis Lake is ringed by diverse terrain, including rock and mud flats around the inlet

The trail is variously faint and overgrown as it runs above the lake and can be tricky to reclaim on the return

Aspen clonal colonies turn color at different times, providing a way to tell each group apart

The Sawatch Range contains 15 fourteeners and 14 centennial thirteeners and is the tallest overall mountain range in Colorado

Long stretches of willow and pockets of aspen in the upper valley make the Big Willis Gulch Trail especially attractive in the fall

While the outlet area is riddled with large boulders, it offers one of the shortest routes off the main trail down to the lake

You'll pass many voluminous cascades on Willis Creek before climbing out of the gulch and into the upper valley

The trail weaves through tall, rocky willow mats with limited visibility from 3.2 - 4.4 miles

Wild blueberries are found in great quantities (sprawling red ground cover) on the flank of Rinker Peak

View from Hope Pass (12,508'), which is accessible by staying on the CDT at the 1.8 mile trail split

The trail climbs 340' in just .35 miles up Big Willis Gulch before moderating in the expansive upper valley