Castle Mound Park is just south of the city of Black River Falls. It is named for the 400 million year-old Cambrian sandstone butte that rises 180 feet above the surrounding sand plain. Cliffs up to 30 feet high chisel the parks central backbone ridge. Boulders litter the forest floor beneath red and white pine, oak, birch, maple and aspen. Plants like large-leaved aster, wintergreen and partridge berry make up the ground layer vegetation. The Red-breasted Nuthatch, pine warbler, solitary vireo and Black-throated Green Warblers are found here. Also seen are Broad-winged Hawks, Ovenbirds and Scarlet Tanagers.