Heron Pond–Little Black Slough Nature Preserve is a protected wetland in southern Illinois near Belknap, within the Cache River basin. Recognized as a National Natural Landmark in 1972 and as a wetland of international importance under the Ramsar Convention, it preserves part of the Cache River drainage and an unusual meeting of landscapes at Illinois’s northern edge of the Gulf Coastal Plain. Its features include limestone bluffs, floodplain, mesic woodland, and wetland forests of old-growth bald cypress and water tupelo. Known for its heron rookery, diverse birdlife, and other wildlife, the 1,861-acre preserve is the largest natural area owned and operated by the Illinois Department of Natural Resources.