The Trylon and the Perisphere were the central structures of the New York World's Fair of 1939-1940. Connected to the Trylon by the Helicline, at the time the world's longest escalator, The Perisphere was a tremendous sphere which housed a diorama called "Democracity" which, in keeping with the fair's theme "The World of Tomorrow", depicted a utopian city-of-the-future. Democracity was viewed from above on a moving sidewalk, under movies displayed on the sides of the sphere.

The concept of the Perisphere was revisited in the later 1964 New York World's Fair with the Unisphere, as well as with Spaceship Earth at Epcot in Walt Disney World.

Built in Flushing Meadows in Queens, New York, both structures were subsequently razed and scrapped for use in World War II armaments.