... ; -lrb- small drawings with each item listed below -rrb- ; -lrb- check -rrb- it takes maintenance workers two months to clean the building 's 6,500 windows. ; -lrb- check -rrb- it snows up at the uppermost reaches of the spire because of wind currents. ; -lrb- check -rrb- floodlights were added in 1964 for the opening of the new york world 's fair and colored lights introduced for the nation 's bicentennial in 1976 . ;