The Bronx Zoo is a zoo located in the Bronx, a borough of New York City, within Bronx Park. It is the largest metropolitan zoo in the United States and among the largest in the world. On average, the zoo has 2.15 million visitors each year and is world-renowned for its large and diverse animal collection, and its award-winning exhibitions. It comprises 265 acres (107 ha) of park lands and naturalistic habitats, through which the Bronx River flows. The zoo is part of an integrated system of four zoos and one aquarium managed by the Wildlife Conservation Society (WCS), and is accredited by the Association of Zoos and Aquariums (AZA).