Willis Tower Skydeck

The building opened in 1973 as the Sears Tower and was the tallest in the world for close to twenty-five years. Its structural idea was Fazlur Rahman Khan's bundled tube system: nine square tubes rising together from the base, with tubes ending at different heights, which is why the profile steps in as it rises and why the frame could go that high with far less steel than earlier designs. The Skydeck is on the 103rd floor at about 412 metres. The Ledge, added in 2009, is a set of glass boxes projecting about 1.2 metres from the face with glass floors, so you stand over a drop of more than four hundred metres. The tower sways measurably in wind and visitors notice.

What you actually see

• The Ledge - glass boxes projecting out with glass floors.
• Floor 103 at about 412 metres - the deck itself.
• A bundled tube structure - nine tubes, ending at different heights.
• Measurable sway in wind - noticeable at the top.

When to go

Year round; clear days only. An hour and a half.

Honest expectations

Cloud makes the ticket worthless with no refund. Queues for the Ledge boxes are long and photos are rushed. Timed tickets are required at peak. It is expensive, and the John Hancock deck is a cheaper alternative with arguably a better view of this building.

Nearby

The Loop and Millennium Park are east; Union Station is west.