The "Great Eyrie" or "Great Nest" in Brownhelm Township was the largest bird-built tree nest ever recorded in Ohio, the fourth in a series of bald eagle nests built over 80-90 years in the same general area along Lake Road between Vermilion and Lorain. Beginning in 1891 and continuing for 35 years, mating bald eagles added sticks to its inverted cone-shaped structure until it reached 12 feet high, 8.5 feet wide, and an estimated weight of two tons. The nest and the area's bald eagles became the focus of a pioneering study of bald eagle behavior by Dr. Francis H. Herrick, a biology professor at Western Reserve University, who spent three springs and summers in the early 1920s recording and photographing the birds and developed unique research methods, including photography as a research tool. In the winter of 1922, he built a ten-foot square tent-like structure on a platform in an elm tree beside the nest, 95 feet above the ground, so he could observe the eagles without disturbing them. His work became the first comprehensive study of the American bald eagle and was published in many forms, including in National Geographic Magazine in 1929. The nest stood 81 feet above the ground in the leaning top of a shellbark hickory tree until the evening of March 10th, 1925, when high winds and heavy rains brought it down. The pair of eagles then built a new nest 13 days later in an oak tree elsewhere in the same grove and raised an eaglet that spring. In 2007, a ground-level replica of The Great Nest was commissioned for the Raptor Center courtyard at the Carlisle Visitor Center, and after that one was dismantled, a new reproduction was built there in 2020 near the site of the original nest.