The Unisphere is a 12-story high, spherical stainless steel representation of the Earth. Located in Flushing Meadows – Corona Park in the borough of Queens, New York City, the Unisphere is one of the borough's most iconic and enduring symbols.

Commissioned to celebrate the beginning of the space age, the Unisphere was conceived and constructed as the theme symbol of the 1964–1965 New York World's Fair. The theme of the World's Fair was "Peace Through Understanding" and the Unisphere represented the theme of global interdependence. It was dedicated to "Man's Achievements on a Shrinking Globe in an Expanding Universe".

[edit] Construction

Designed by landscape architect Gilmore D. Clarke, the Unisphere was donated by the United States Steel Corporation and constructed by the American Bridge Company. It is the world's largest global structure, rising 140 feet and weighing 700,000 pounds. Some sources say the Unisphere weighs 900,000 pounds, a figure which includes the additional weight of its 100-ton inverted tripod base. The diameter of the sphere itself is 120 feet, or 36.57 meters. It is constructed of Type 304L stainless steel.

Built on the structural foundation that supported the Perisphere of the 1939–1940 New York World's Fair, the Unisphere is centered in a large, circular reflecting pool and is surrounded by a series of water-jet fountains designed to obscure its tripod pedestal. The effect is meant to make Unisphere appear as if it is floating in space.

During the fair, dramatic lighting at night gave the effect of sunrise moving over the surface of the globe. Additionally, the capitals of nations were marked by uniquely designed lights that held four bulbs each. One of these lights is placed at the location of the Kahnawake Indian Reservation, which the Mohawk ironworkers requested to be placed there to honor their labor.[1] When one would burn out, another would rotate in place so that the bulbs would not have to be changed during the two-year run of the Fair. None of these lighting effects are still in operation.

Three large orbit rings of stainless steel encircle the Unisphere at various angles. These orbit rings are believed to represent the tracks of Yuri Gagarin, the first man in space, John Glenn, the first American to orbit the Earth, and Telstar, the first active communications satellite. In fact, the early design was to have a ring for each of a dozen satellites in place at the time of the Fair. This proved impractical not only in the number of satellites, but also in the height of their orbits and the fact that geostationary satellites had no orbit path. As a result a symbolic number of three was chosen for aesthetic reasons.

[edit] Rehabilitation

In 1989, the New York City Department of Parks and Recreation announced a multi-million dollar rehabilitation of Flushing Meadows-Corona Park. Among the projects was a complete restoration of the Unisphere. Begun in late 1993 and completed on May 31, 1994, the project included numerous structural repairs and removal of years' worth of grime which had accumulated on the steel. The fountains, which had been shut off since the 1970s, were replaced, and new floodlighting was installed.

On May 10, 1995, the Unisphere was given official landmark status by the New York City Landmarks Preservation Commission. It is the only officially designated landmark in Flushing Meadows-Corona Park.

The Unisphere's fountain reopened on August 12, 2010, after a $2 million restoration of its pumps, valves and paintwork.[2]

The newly built Unisphere during the 1964-1965 World's Fair

[edit] Structural foundation

The marshy soil of Flushing Meadows needed special consideration during the original 1937 Perisphere construction for the 1939 World's Fair. The Perisphere, and subsequently the Unisphere, which used the same platform, employed a foundation of 528 pressure-creosoted Douglas fir piles of 95 to 100 feet in length. Before construction of the Unisphere, three piles were tested for structural integrity and all were found to be sound throughout their entire length.[3]