Parfrey's Glen, Wisconsin's first State Natural Area, is a spectacular gorge deeply incised into the sandstone conglomerate of the south flank of the Baraboo Hills. The exposed Cambrian strata provide excellent opportunities for geological interpretation. The walls of the glen - a Scottish word for a narrow, rocky ravine - are sandstone with embedded pebbles and boulders of quartzite. The moss-covered walls are moist from seepage, cool and shaded. As a result, they support a flora more typical of northern Wisconsin with yellow birch, mountain maple, and red elder and several rare plant species, including the federally threatened northern monkshood (Aconitum noveboracense) and state-threatened round stemmed false foxglove (Agalinus gattingeri). Other rare species are cliff goldenrod (Solidago sciaphila), and two state-threatened birds, the cerulean warbler (Dendroica cerulea) and Acadian flycatcher (Empidonax virescens). Parfrey's Glen Creek, a fast, cold, hardwater stream flows through the gorge and harbors a very diverse insect fauna including a rare species of diving beetle (Agabus confusus) and a rare caddisfly (Limnephilus rossi). Parfrey's Glen is owned by the DNR and was designated a State Natural Area in 1952.