My friend is visiting Chicago! What should we do while in the city?

Hi! My friend is visiting on August 1st and staying for four days. What can we do for low cost or for free in Chicago (we’re in our twenties and have no money). We both dislike nature, love movies, love art, love theater, love architecture, love vintage anything, but especially clothes.

By the way, me saying we hate nature is mostly tongue in cheek…we don’t actually hate nature; I just don’t want a dozen replies saying go this or that park.

Thanks! Xx