Head back down Jackson a short ways west to Dearborn Street and you'll find yourself in front of the Monadnock Building. At 197 feet tall and constructed in 1893, it's largely recognized as the world's first skyscraper. Even if some might find that debatable, what is a fact is that it's the tallest building fully supported by masonry walls unlike the steel supports used today.
The walls at the bottom of the building are 6 feet thick in order to handle the building's massive weight. The outer walls then curve in a bit and go straight up before curving back out at the top. That curve, plus slight bay windows, are the only ornamentation of note on the building.