The Cincinnati Zoo and Botanical Garden is ranked as one of the top zoos in the country.  Opened in 1875, it is the nation's 2nd oldest zoo and a national historic landmark.  The Zoo's 75 acres house 510 animal species and 3,000 plant varieties.  This not-for-profit entity is internationally known for it's success in the protection and propagation of endangered animals and plants, and engages in research and conservation projects around the world.