At 1,451 feet (443 metres) the Willis Tower — until 2013 the tallest building in the Western Hemisphere — remains the tallest building in Chicago and one of the most recognisable examples of structural engineering from the late 20th century. The Skydeck on the 103rd floor offers 360-degree views across the city, Lake Michigan, and (on clear days) four surrounding states.
The transparent glass ledge boxes that extend four feet from the building are the most discussed feature; the views without them are actually better. The queue can be long on peak summer days; booking ahead is strongly recommended. The building itself is worth circling at street level — the bundled tube structural system visible in the corners of the facade is the engineering solution that made the height possible. Adams at Wacker.