where is the biggest zoo in the world

The Berlin Zoological Garden was opened in 1844 and is the oldest zoo in Germany. Located in Berlin’s Tiergarten, the zoo is home to 1,500 species and 19,500 total animals. At this number, the Berlin Zoological Garden holds the most comprehensive collection of species in the world. The zoo is considered to be the most visited zoo in Europe and among one of the most popular zoos worldwide