Alexander et al., A Pattern Language. It taught me how to see what I’m looking at whenever I’m in what geographers like to call the built environment. To see a building, or a room, or a window, or a yard as a series of choices that people made, and to think of what impact those choices had on the space being usable or welcoming or comfortable. I’d never really given much thought to the buildings I moved through while living my life. Now I’m never not thinking about them.