Neda Mine, an abandoned iron mine located on the Niagara Escarpment near Mayville and Horicon, Wisconsin, is among the largest bat hibernacula in the Midwest. The property was acquired by the University of Wisconsin-Milwaukee in 1976; at that time an estimated 75,000 bats were using the mine. By 2005 up to 150,000 bats of four species (Little brown bats, Big brown bats, Eastern pipistrelles, and Northern long-eared bats) were using the hibernaculum. The fungus that causes white-nose syndrome (WNS) in bats was first detected at Neda Mine in 2015. The disease was confirmed in the bat population in 2016, and the population of bats in the mine has declined.
The mine is also of geological interest; its cliffs provide an excellent exposure of the Niagara Dolomite and the only accessible exposure of the Neda Iron formation. Nearby, Neda Beechwoods lies on the escarpment and is a well-developed beech stand at the western boundary of beech.