The Berlin U-Bahn, like the New York subway, is a surprisingly easy place to feel alone. People avoid eye contact in the crush, and the German announcer’s voice has a lilting softness at odds with the language’s guttural reputation. For the year I lived in Berlin, the U-Bahn was where I spent time in my own head, easing into the day. It was unusual when, riding the U1 through Kreuzberg, my faux-solitude was interrupted by the onset of paranoia. More…