Massive and Rigid...
This building is all about mass and rigidity. It's shear mass can make it overwhelming at times, but in that massiveness is a beautiful simplicity in it's engineering.
This building is essentially nine skyscrapers of varying heights bundled together to form one huge one. This makes for a super duper strong structure that isn't likely to go anywhere any time soon.
Those of us who live here and see it on a daily basis tend to take it for granted that it is among the tallest structures on the planet. I am often amused by the tourists wandering the Loop searching for it, and looking on their guide maps.