My heart actually skipped a beat when I opened the file on my iPhone. I might have even gasped. Here, in three dimensions and full colour was “Model 57” from 1947, and I could go from a bird’s-eye view to a close-up of the front door with a flick of my finger. I could spin the little house around as if it was on a turntable to view all sides in seconds, or I could walk, slowly, down the hallway and peek into every room.