My son and I backpacked to Ptarmigan Lake near Cottonwood Pass last week. The lake is above treelike in a small valley in the Collegiate Peaks wilderness. The hike itself is relatively short which makes for a fun out and back. We were treated to a beautiful sunset.
To reach Ptarmigan Lake, drive 14 miles west of Buena Vista on Rd 306 (Cottonwood Pass). There is a sign for the parking lot on the left.. Hike south through the forest for 2 miles. The trail climbs steeply at first for the first 1/2 mile and crosses a couple of boulder fields. The levels off some over the next 1.5 miles. Around mile 2 it climbs a couple of switchbacks and you finally have some views of the surrounding mountains. A small tarn is on your right and a lake is off to the left. Continue for about 3/4 mile past the small tarn on the right before steeply ascending the last 300 feet to Ptarmigan Lake. There are several small tarn and lakes in this area. I found the one just to the left of Ptarmigan Lake to be the prettiest. You are above treelike here so caution may be warranted if storms are in the area.