Artist's conception of an Entrance Gate to the Fair.
Source: New York World's Fair 1964-1965 Corporation Progress Report #8
April 22, 1963

Artist's conception

The 80-foot high tower at the Gotham Plaza Gate.
Source: On-line auction (eBay)

Backbone of the Fair? No, one of the spiny columns marking the entrances and exits to the grounds.
Source: News Colorfoto by Daniel Jacino
Source: New York Sunday News - April, 1964