Mountains

A 25-Acre Nature Preserve Tucked Behind the Aspen Post Office

Water and land Pitkin County Aspen family wildlife birding

Most of Aspen’s outdoor reputation lives up high, in wilderness that asks for boots, breath, and a long drive. Hallam Lake is the opposite. It sits at the end of Puppy Smith Street, behind the post office, a short walk from the heart of town.

This 25-acre nature preserve is the home base of the Aspen Center for Environmental Studies, known as ACES. Elizabeth Paepcke donated the land in 1968, and it has been a quiet pocket of valley ecology ever since. A half-mile loop trail is open to all visitors year-round. It winds in and out of wetlands and aspen forest, the kind of habitat where mule deer, beavers, foxes, songbirds, and golden eagles turn up.

It is a gentle way to meet the Roaring Fork Valley, especially with kids. The walking is easy, the boardwalks keep you out of the mud, and an on-site naturalist is on hand to answer questions. ACES also keeps live birds of prey here as education ambassadors and runs guided walks through the seasons, plus snowshoe tours elsewhere in the valley once the snow arrives.

Programs, hours, and any fees change with the season, so check the official ACES page before you go: https://aspennature.org/locations/hallam-lake/

Sources

Official or primary sources used for this note. Local details can change, so confirm before acting.

Reviewed: June 15, 2026 Aspen Center for Environmental Studies — Hallam Lake

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