A beaver dam is made of rocks, logs, branches, and mud. These materials stop the flow of the stream and create a large, still pond. Find out more in Beaver Dams, a title in the Nature’s Engineers series. Nature’s Engineers is a series of AV2 media enhanced books. Each title in the series features easy-to-read text, stunning visuals, and a challenging educational activity. A unique book code printed on page 2 unlocks multimedia content. These books come alive with video, audio, weblinks, slideshows, activities, hands-on experiments, and much more.