Please note: New entrance/exit patterns. Main Entrance (Vehicles and Pedestrians): 3001 Connecticut Ave. NW Alternative Entrance (Pedestrians Only): Harvard Street Bridge The Smithsonian’s National Zoo and Conservation Biology Institute leads the Smithsonian's global efforts to save species, better understand ecosystems and train future generations of conservationists. Its two campuses are home to more than 2,000 animals, including critically endangered species. Always free of charge, the Zoo's 163-acre park in the heart of Washington, D.C., is a popular tourist destination. The Zoo instills a lifelong commitment to conservation through engaging experiences with animals and the people working to save them.