There are several categories that decide what is the world’s biggest zoo. Things like number of animals, species, land area etc.
Although there are somewhat bigger zoos in the terms of land area or number of species, when you combine these categories and the number of animals there is only one zoo that stands out – Hendry Doorly Zoo, located in Omaha, Nebraska. This is also the biggest zoo in the United States.
Henry Doorly Zoo and Aquarium is home to about 17,000 animals with more than 960 different species. It was opened in 1894, and it covers the area of over 130 acres (53 ha). The Zoo is Nebraska’s number one paid attraction and it was visited by more than 25 million people over the past 40 years. It also features the world’s largest indoor swamp, the world’s largest indoor desert that cost around $31.5 million to build.