Thomas Lakes is a stop at 3.9 miles, just below treeline, on the full hike and steep ascent of Mt. Sopris–which is 12.9 miles out and back. There are two lakes about a quarter-mile apart with designated camping in between.
Difficulty: Moderate to the lakes; difficult to the summit (through talus and scree fields and steep terrain)
From Basalt to the Trailhead: Take Hwy. 82 northwest from Basalt to the Carbondale exit. From Carbondale, travel south on Hwy. 133 for 1.4 miles. Make a left on Prince Creek Rd. and go about six miles to the fork in the road. Take a right at the fork and follow it for two miles. The trailhead is a quarter-mile before Dinkle Lake, across from the fenced parking area.
More here from Aspen Trail Finder as well as additional information from Forest Service.