There are game reserves in Africa that might be considered huge open-air zoos. The largest of these is Namibia, in Southwest Africa. This huge zoo covers 78,000 square miles, about the size of the state of Virginia!
The zoo that attracts the most visitors, however, is in Mexico City, Mexico. More than five million people visit this zoo each year.
The zoo with the greatest number of species, though, is in West Berlin, Germany. This zoo exhibits more than 2,300 different animals!
The oldest zoo still in existence today is the Schonbrunn Zoo, in Vienna, Austria, open since 1752!