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 (29 to 30 m) 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.[9]