Baxter's Hollow features a scenic gorge cut through Baraboo quartzite by Otter Creek, a fast, clear, nearly undisturbed stream flowing over the large quartzite boulders. Although it supports trout, Otter Creek is better known for its diverse and unique aquatic insect fauna including at least 78 species of caddisfly. Cold air drainage has permitted a white pine dominated forest to persist near the stream. Understory species on the boulder-strewn slopes are large-leaved aster, marginal wood fern, partridgeberry, sweet cicely, witch hazel, and squawroot. Most of the site, though, contains a significant portion of the Big Woods, the largest intact contiguous southern dry-mesic forest in Wisconsin with red and white oak, hickory, and basswood. In spring, the forest floor is blanketed with a wide variety of colorful flowers including spring-beauty, Jacob's-ladder, trillium, hepatica, shooting-star, dog-tooth violet, and marsh marigold. The large expanse of woods provides critical habitat for many rare bird species that require large forested tracts including the state endangered worm-eating warbler and state threatened Kentucky and hooded warbler. The combined effects of microclimate and different communities have allowed a wide diversity of species to flourish here: 39 mammals, 92 breeding birds, 13 amphibians, and 18 reptile species. Baxter's Hollow is owned by The Nature Conservancy and was designated a State Natural Area in 1970.