233 S. Wacker Drive. Architects were Skidmore, Owings & Merrill. Built in 1974, it was recognized as the tallest building in the world. Even though the building has been surpassed in height by the Petronas Towers in Kuala Lumpur, it is considered one of Chicago's finest buildings. A popular tourist attraction, the observation deck offers a panoramic view of up to 50 miles from the 103rd floor. Daily. 312-875-9696.