Aspen Center for Environmental Studies (ACES) Description

Aspen Center for Environmental Studies operates Hallam Lake, a 25-acre nature preserve and its founding campus, at 100 Puppy Smith Street in Aspen’s West End neighborhood. Aspen Center for Environmental Studies keeps Hallam Lake open to the public free of charge year round, giving families, students, and casual visitors a chance to walk trails through wetlands and riparian habitat just minutes from downtown without ever paying an admission fee.

Elizabeth Paepcke founded Aspen Center for Environmental Studies in 1968 and donated the Hallam Lake property the following year, setting the organization on a path that has since grown well beyond its original Aspen campus. Aspen Center for Environmental Studies now also runs Rock Bottom Ranch, a 113-acre working farm and wildlife preserve in Basalt focused on regenerative agriculture, along with the Catto Center at Toklat, a remote high-alpine site in Castle Creek Valley once home to ACES founder Stuart Mace. Back at Hallam Lake, the campus includes self-guided nature trails, an indoor trout stream, and enclosures that house resident birds of prey unable to survive in the wild, including golden eagles and great horned owls, giving visitors a close look at species they would rarely encounter otherwise.

Programming runs daily and spans the full calendar, from guided nature walks and birdwatching outings to youth science camps, teacher training, and evening programs like sunset beaver walks that dig into local river ecology. Naturalist staff also lead forest health initiatives, land restoration projects, and school partnerships across the valley, extending the organization’s reach well past its three physical campuses. Between Hallam Lake, Rock Bottom Ranch, and Toklat, Aspen Center for Environmental Studies covers a wider range of Rocky Mountain ecosystems than any comparable organization in the region, all built around the same mission Paepcke set out more than five decades ago.

Category: Outdoor
Features: Family, Events, Hiking, Historical Sites, Nature
Address: 100 Puppy Smith St, Aspen, CO 81611
Directions: View on Google Maps