Mills Lake and Jewel Lake lie at the gateway to an iconic glacial valley in Rocky Mountain National Park. Further up valley is Black Lake, which fills a deep cirque fed by the slopes of McHenrys Peak (13,327'), Chiefs Head Peak (13,579') and The Spearhead (12,575'). Unmaintained routes continue above Black Lake to Blue Lake, Green Lake and Frozen Lake.

The trail climbs beside Ribbon Falls on the final push to Black Lake

Looking over Black Lake from the precipitous outlet of Frozen Lake in the upper valley

A glacier is defined as a perennial mass of snow or ice that's large and heavy enough to flow like a thick gel; glaciers form wherever more snow accumulates than is lost each year

Black Lake fills a deep, steep-walled cirque at treeline in Glacier Gorge

Peaks of the Mummy Range emerge to the north early in the climb from Glacier Gorge Trailhead

Concentrations of 3200 elk in summer may dwindle to 1000 during winter as they migrate to lower elevations and move outside the Park

Glacier Gorge was carved by a 'valley glacier'; only cirque glaciers remain in the Park today

There are no 'valley glaciers' in RMNP today, but 15,000 years ago many of the Park's valleys were filled with ice

Mills Lake is the first of 5 spectacular alpine lakes in Glacier Gorge, remnants of the Park's active glacial past

Young aspen line sections of Glacier Creek near Alberta Falls

Jewel Lake from its marshy outlet

Alberta Falls

The Mills Lake Trail sees heavy use throughout the winter, and sometimes only poles and basic traction devices are needed to reach it

Mills Lake from its south shore

A cirque glacier is a small glacier that fills a bowl-shaped basin at the head of a mountain valley