Willis Tower

Where it sits. The tower stands at 233 South Wacker Drive on the western edge of the Chicago Loop, where the river bends south and the financial district gives way to Union Station and the expressway. It rises 442 metres to the roof and 527 metres to the tip of its western antenna, and it is visible from most of the flat country around the city — on a genuinely clear day the observation deck takes in parts of Illinois, Indiana, Michigan and Wisconsin, though the four-state claim needs unusual air to be honest. The plaza at its base is unloved and windy; the building is best appreciated from a distance, from the river walk, or from Adams Street looking west, where the bundled shafts stack against the sky.

How it was built. Sears, Roebuck and Company commissioned it as headquarters for what was then the largest retailer in the world, and Skidmore, Owings and Merrill delivered it in 1973. The structural idea belongs to Fazlur Rahman Khan, the Bangladeshi-American engineer who had already worked out the framed tube at the John Hancock Center. Here he assembled nine square tubes, each 23 metres on a side, into a single 68-metre-square bundle, then terminated them at different heights: two stop at the fiftieth floor, two more at the sixty-sixth, three at the ninetieth, and two continue to the top. The result is a building that carries its own wind load through its skin, uses dramatically less steel than a conventional frame of that height, and gets its distinctive stepped silhouette from pure structural logic rather than styling. The cladding is black anodised aluminium and bronze-tinted glass.

On screen. In Ferris Bueller's Day Off (1986), Ferris, Cameron and Sloane ride to the top of what was then the Sears Tower, press their foreheads against the glass and look straight down at the street. John Hughes shot the sequence on the 103rd-floor Skydeck itself, and the scene is a fair record of what that floor was like before the 2009 alterations: plain windows, a low sill, and nothing between the visitor and the drop but a pane. The glass balconies that everyone now queues for did not exist when the film was made, so anyone recreating the shot is standing in a different room. Hughes used the tower as the vertical counterpoint to the day's other stops — the trading floor, the Art Institute and the parade — in a film that functions, deliberately, as a civic advertisement for Chicago.

The Ledge and the record. For twenty-five years this was the tallest building in the world, from its 1973 completion until Kuala Lumpur's Petronas Towers took the title in 1998 on a ruling that counted architectural spires — the Chicago building's roof and highest occupied floor both remained higher, which is why the decision still rankles locally. It was renamed Willis Tower in 2009 after the London insurance broker Willis Group Holdings took a lease and the naming rights. The same year, four glass boxes called the Ledge were cantilevered 1.3 metres out from the 103rd floor, with glass floors 412 metres above Wacker Drive. Below them, a 2018 remodelling added a retail and dining base called Catalog and a rooftop terrace on the fifth floor.

What a visit involves. Skydeck entry is through a separate lower-level entrance on Jackson Boulevard, and the route runs through an exhibition on Chicago's building history before the lift, which climbs to the 103rd floor in about a minute. Queues at midday in July can exceed an hour even with timed tickets; opening time and the last ninety minutes are far better, and the last slot of the evening gives you the city lighting up. Weather matters more here than at most attractions — low cloud can close the deck entirely and haze flattens the view — so a flexible ticket is worth more than a cheap one.

Getting there and what to pair it with. Quincy on the Brown, Orange, Pink and Purple lines is two blocks east and is itself worth seeing, a restored 1897 elevated station with its original Victorian ironwork. Union Station and Ogilvie are both within ten minutes on foot. The obvious pairing is a comparison with the John Hancock Center's observatory on North Michigan Avenue, which is lower but sits closer to the lake and gives the better skyline photograph, since it looks back at this tower rather than standing on it. For architecture without a ticket, the Chicago Architecture Center's river cruise passes the tower's base and explains Khan's bundled tube from water level, which is where the stepped profile makes the most sense.