Speaking of metaphors...
...I was surprised to read that the tower's going to be mostly residential. The shape seems to strongly evoke the notion of a "cathedral to commerce", and I expected to read that it was going to consolidate all of Chicago's oligarchs in one place. Oil speculators in their penthouse suites at floors 140 and above, speculators in food and other necessities 130+, mortgage companies at 120, advertising firms 80-120, and so on, in sort of linear/vertical rendition of Dante's circles. No doubt the first few floors will contain a retail mall.