> OpenTTD is interesting because it can have multiple "cameras" following objects on the screen. e.g. a viewport can be opened to follow a bus or train, zoomed in, while the main viewport is zoomed out.

I have used OpenTTD, so I don’t know the specifics, but from how you describe it, RollerCoaster Tycoon has/had this too. The main viewport would show what you’re zoomed in/out on, while you could have a screen open following a roller coaster train.