Mirror Lake is a small Forest Service reservoir just downstream of Blanchard Springs, fed by the same impossibly clear spring water that gives the lake its name and its temperature — cold enough year-round to keep stocked trout fishing reliable. The lake is small, oval, and ringed by a paved trail that gets you around the whole circuit in twenty minutes.
A small rebuilt 19th-century gristmill on the dam at the lake's outflow gives the area its name on the National Register as a historic district. The recreation area has a swimming beach, a campground, and pull-offs for picnic stops. Combine with the Blanchard Springs cave tours for a full half-day in the national forest.