One of my big thrills is when I encounter something in real life that I first read in a book. For instance, in sixth grade, I was gobsmacked when I realized that the mitochondria in Madeline L'Engle's The Wind in the Door were real parts of our cells. (Of course, the teacher had no idea what I was talking about when I asked for the farandolae.)
I happened across this picture at the Shorpy blog, which posts historical photographs, and instantly thought of Karen Hesse's 2008 MG novel, Brooklyn Bridge, which takes place during the building of New York's favorite river-crossing apparatus. I keep squinting at the background to spot one of the kids under the bridge.