3) The Sears Tower was constructed in 1973 to house all workers of the largest retailer at the time, the Sears Roebuck & Co. Over the years, it has seen Taipei 101 and the Petronas Towers surpass it but by the measurement from the ground to the top of the antenna/spire it is still the tallest building in the world.
They say on a clear day you can see four states; Illinois, Indiana, Wisconsin, and Michigan. Fantastic fact: And just in case you need a better view the building has six robotic window-washing machines mounted on the roof.
A good view from the Sears Tower can be found below and I have never seen so many happy employees.
And yes, in 1999 French Alain "Spiderman" Robert scaled the building's exterior glass and steel wall all the way to the top...without getting caught.