The San Diego Zoo is a zoo in Balboa Park, San Diego, California, housing over 3,700 animals of more than 650 species and subspecies. Its parent organization, San Diego Zoo Global, is one of the largest zoological membership associations in the world, with more than 250,000 member households and 130,000 child memberships, representing more than a half million people. The San Diego Zoo was a pioneer in the concept of open-air, cageless exhibits that re-create natural animal habitats.