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.