zoological garden or zoo, public or private park where living animals are kept for exhibition and study. The menageries and aviaries of China, Egypt, and Rome were famous in ancient times. From the late medieval period many rulers had private menageries, some of which later formed the nucleus of public exhibits. Nearly all large cities now have zoological reserves. Notable ones include those of London (Regent's Park), Paris (Jardin des Plantes and Jardin d'Acclimatation, Bois de Boulogne), Berlin (Tiergarten), Toronto (Metro), New York City (Bronx), Chicago (Lincoln Park and Brookfield), Cincinnati, Detroit, Philadelphia, St. Louis, and San Diego (Balboa Park). Modern trends include breeding endangered animals in captivity (some have been reintroduced into the wild), exhibiting animals in enclosures simulating their natural habitat rather than in cages (open-range zones or safari parks), and educating the public about the principles of ecology.