View over Tyndall Glacier and Flattop Mountain from the approach to Hallett Peak

The Flattop Mountain Trail follows a similar route used by indigenous Ute to cross the Continental Divide

View of Taylor Peak from open tundra at the base of Hallett Peak

A ptarmigan transitions into winter plummage

The Mummy Range nudges over the northern horizon on the final approach to Flattop Mountain

In the open tundra, large rocks that provide a modicum of wind shelter are rare

Marmot burrows average 3-5' deep, but can reach 15-20' in preparation for the winter hibernation

Southwest view of Andrews Peak from Hallett Peak

Looking south over Chaos Canyon toward Otis Peak, Taylor Peak, and Longs Peak from Hallett Peak

A hiker approaches the Tyndall Glacier gorge below Hallett Peak on the approach to Flattop Mountain

Vista from Flattop Mountain. There's no 'summit' to Flattop, rather a wide flat expanse of tundra marks the area

A well-established cross-country route leads from Flattop Mountain to the base of Hallett Peak

Looking north at Notchtop and Thatchtop on the ascent to Flattop Mountain

Below Hallet Peak is one of the park's few named glaciers - Tyndall Glacier

Ptarmigan are common in the rocky tundra, but exceptional camouflage makes them difficult to spot

Many flowering plants of the tundra have dense hairs on stems and leaves for wind protection

Hallett Peak and Longs Peak seen from the gorge rim carved by Tyndall Glacier, one of five active glaciers in the Park

Westerly view of the Never Summer Range from Flattop Mountain

Plants of the tundra have pigments capable of converting the sun's light rays into heat