Glen Helen Nature Preserve — Public Lands Institute

Geological age: ~445–430 million years ago (bedrock); gorge and ravine system formed by glacial meltwater ~15,000 years ago
Epoch: Silurian period (Llandovery–Wenlock); same dolomite and limestone formations as Clifton Gorge; Holocene iron precipitation at Yellow Spring actively ongoing — visible as orange mineral staining on rock surfaces
Native lands: Shawnee (Shawanwaki) · Miami · Adena culture; Orators Mound (Adena burial mound) within preserve boundaries; Yellow Spring a known Shawnee waypoint; Little Miami River a principal Shawnee waterway
Ecology: Mixed mesophytic gorge forest; 400-year-old trees; regionally significant old-growth stands; beaver wetland; Raptor Center (Ohio’s first raptor rehabilitation facility); 20+ miles of trail connecting to John Bryan State Park and Clifton Gorge
Hydrology: Little Miami River (2.5 miles; National Wild & Scenic River); Yellow Spring Creek; Birch Creek; iron-rich Yellow Spring seep; beaver impoundment; Cascades waterfall
Acreage: 1,147 acres
Conservation: Private nature preserve (Antioch College); National Natural Landmark; National Wild and Scenic River (Little Miami River); Ohio State Scenic River (Little Miami River)
Endangered species: none documented
GPS: 39.8030° N, 83.8910° W