The dominant feature at Pewits Nest is a 30- to 40-foot deep gorge formed during the retreat of the last glacier. Associated with it are Skillet Creek, shaded cliffs, and a northern dry-mesic forest. When Glacial Lake Baraboo drained, Skillet Creek cut a narrow canyon through the Cambrian sandstone, forming a series of potholes and waterfalls. The layers of Cambrian sandstone show that a finer-grained sediment was laid down by the Cambrian seas "inside" the syncline, a process different from that at Parfrey's Glen where coarser Cambrian conglomerates and sandstones are found in layers. Forest cover includes red cedar, white pine, hemlock, and yellow birch.