Although zoos', of which dictionary meaning is asite designed to expose wild animals and pets, roots go back 18th century, it is actually known that roots of animal collecting go back more far. Despite the fact that animals should be left İn ıheir natural habitat, zoos became essential facilities because of aspiration and wonderment of human being for the nature and its elements. Planning and design principles should be well known and implemented not only for health and comfort of animals but also for security and satisfaction of human who wants to get knowledge about the animals. In this study definition, historical development, functions, and aims of zoos are reviewed; planning and design principles of these sites are investigated.