men arrived in 1521. Also the Raven Cage (created in 1829), is regarded as one of the oldest structures in the London Zoo. Victorian revival The first large aviary inside a zoological garden was established in 1880 in the setting of the Rotterdam Zoo. Aviaries were an important aspect for the many Rothschild houses that proliferated across Europe in the 19th century. This was a recalling of the aristocratic custom from the late 1600s, which involved the elite society displaying their power, status and wealth through the exhibition of exotic birds and animals. For instance, Baron Ferdinand de Rothschild built his aviary in 1889 at Waddesdon Manor, UK, erected in the style of Versailles' trelliswork pavilions. 20th century to modern day In 1902, a flying cage was completed in the setting of the National Zoological Park of the Smithsonian Institution. A new Great Flying Cage was built in 1964. The Saint Louis Zoo is home to the 1904 World's Fair Flight Cage. It is one of only two permanent structures built for the World's Fair which still remain (the other is the Saint Louis Art Museum's Cass Gilbert building). In 1904, it was the largest bird cage ever built. It remains one of the world's largest free-flight aviaries. The long, wide, and high cage was built by the Smithsonian Institution specifically for the St. Louis World's Fair. Local pride in the giant cage motivated St. Louis to finally establish a zoo in 1910. In 1937, the San Diego Zoo's aviary designed by architect Louis John Gill opened; it was then the largest in the world. The mammoth steel structure, long, wide and more than high, funded by the Works Progress Administration at a cost of $50,000, had no beams, cross or guy-wires to impede the flight of the birds. With the Antwerp cage system (1948), birds are only separate from public with a light system used indoor the Bird Building at Antwerp Zoo. At the Frankfurt Zoo, the bird house was built in 1969. Its Bird Halls presented birds for the first time in large glassed miniature habitats. In diving exhibits, darters and kingfishers could be seen hunting under water, and in the free-flight hall visitors still walk amongst tropical birds in dense vegetation. In 1963, the same principle was used outdoors to construct the Bird Thicket, ten aviaries surrounded by dense bushes and designed in various habitat settings, which