The Zoo's trails - How everything began ...
The unrestricted keeping of wildlife began during the Palaeolithic Age. Animals were kept in primitive enclosures or pits, mainly as living food stock. Young or sick animals were nursed and carefully looked after which led to their domestication. At the beginning of the Middle Ages, menageries were added to courts, castles and palaces in Europe. Mostly bears or other indigenous predators were held in narrow pits, kennels or ditches. Around 1300 A.D. Marco Polo discovered the biggest zoo of that time. He found it at the court of Kublai Khan in Xanadu (Aztec Empire). Unfortunately this zoo was destroyed by Spanish conquerors in 1519.
Animal keeping also served spiritual purposes. In the Orient, it was wide spread amongst sects and religious groups to keep animals in temples or sacred groves.
Individual animals as well as whole herds were held to eventually be sacrificed. During the second century B.C. Egyptian kings established the first so-called 'animal gardens' to demonstrate their power and wealth. Around this time zoological gardens also emerged in China. The most famous one of them was the "Garden of Wisdom". One attraction of this garden were Milus that had already become extinct in their natural environments. The establishment of zoological gardens went hand in hand with the organization of expeditions that had only one intention: catching animals for zoos.
From Greek culture the Romans learnt a lot about zoo traditions. They also had numerous private zoos and special enclosures. Unfortunately, the Romans also misused animals. They drove wild animals into public arenas where they mutilated each other or fought with slaves to amuse the spectators.
The oldest zoo of modern form which still exists today is located in Vienna, Schönbrunn. It was commissioned in 1752 by Emperor Franz II. and Empress Maria Theresia. After the French Revolution, zoological gardens which until then had only served to entertain the upper class were opened to the general public.
The focus was shifted towards education and recreation. Travelling menageries which showed their animals at funfairs and trade exhibitions played a minor role in the history of zoos. They were more important for the history of circuses.

Some more facts: 
1739 first zoo (in Paris)
1828 first zoological garden set up by the "Zoological Society" in Regent´s Park, London
1844 first zoo in Germany (in Berlin), influenced by Alexander von Humboldt
1907 first open-air enclosures using moats and no disturbing barriers in Hamburg, designed by Karl Hagenbeck
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