sentence1: Its construction for the World's Fair of 1889 was an astounding engineering achievement ' 18,000 pieces joined together by 2,500,000 rivets, soaring 300 m (984 ft) into the air but standing on a base that is only 130 m (1,400 ft) square.
sentence2: Its construction was for the World's Fair of 2002, and was a small engineering feat.