The Saint Louis Zoological Park, commonly known as the St. Louis Zoo, is a zoo in Forest Park in St. Louis, Missouri. It is recognized as a leading zoo in animal management, research, conservation, and education. Admission is free based on a public subsidy from a cultural tax district, the Metropolitan Zoological Park and Museum District (ZMD); fees are charged for some special attractions. A special feature is the Zooline Railroad, a small passenger train that encircles the zoo, stopping at the more popular attractions. The city purchased its first exhibit, the Flight Cage, from the Smithsonian Institution following the 1904 St. Louis World's Fair. After the zoo was established, new exhibits, areas and buildings were added through the decades to improve care of the animals, the range of animals and habitats shown, as well as education and interpretation.