9. The San Diego Zoo
Location: Balboa Park, San Diego, California, United States of America
Number of Animal Species: 650
Number of Animals: 3,700
Notable Species: Cougars, panda bears, polar bears, gorillas, koalas, wombats, wallabies and Tasmanian devils.
Opening: 1916
Features: Open-air exhibits without caging, gondola lift (Skyfari), tour buses, and natural habitat recreation.
Size: 100 acres